EXCHANGE 


BOBl'12  W1W 


SILICIC  ACID,  ITS  INFLUENCE  AND  REMOVAL 
IN  WATER  PURIFICATION 

BY 

OTTO  MITCHELL  SMITH 

B.  S.  Drury  College,  1907 
M.  S.  University  of  Illinois,  1918 


THESIS 

Submitted  in  Partial  Fulfillment  of  the  Requirements  for  the 

Degree  of 

DOCTOR  OF  PHILOSOPHY 

IN  CHEMISTRY 
IN 

THE  GRADUATE  SCHOOL 

OF  THE 

UNIVERSITY  OF  ILLINOIS 

1919 
[Printed  by  authority  of  the  State  of  Illinois.] 


SILICIC  ACID,   ITS  INFLUENCE  AND  REMOVAL 
IN  WATER  PURIFICATION 

BY 

OTTO  MITCHELL  SMITH 

B.  S.  Drury  College,  1907 
M.  S.  University  of  Illinois,  1918 


THESIS 

Submitted  in  Partial  Fulfillment  of  the  Requirements  for  the 

Degree  of 

DOCTOR  OF  PHILOSOPHY 
IN  CHEMISTRY 


IN 
.       THE  GRADUATE  SCHOOL 

OF  THE 

UNIVERSITY  OF  ILLINOIS 

1919 

[Printed  by  authority  of  the  State  of  Illinois.] 


-n 


ACKNOWLEDGMENT. 


^  The  writer  wishes  to  express  his  gratitude  to  Professor  W.  F.  Mon- 
jflrt  and  Lieutenant-colonel  Edward  Bartow,  under  whose  direction  this 
investigation  was  made,  for  their  interest  and  many  helpful  suggestions 
during  the  progress  of  this  work  and  the  preparation  of  the  manuscript 
of  this  thesis.  He  also  desires  to  thank  Mr.  G.  C.  Habermeyer,  mem- 
bers of  the  University  faculty  of  the  Department  of  Chemistry  and  the 
Water  Survey  staff  for  their  kind  assistance. 


SPRINGFIELD,  ILL. 

ILLINOIS  STATE  JOURNAL  Co.,  STATE  PRINTERS. 
1921 

34613—100 


CONTENTS. 

PAGE. 

Acknowledgment    2 

Introduction    5 

Theoretical    and    Historical    Part 6 

The  distinguishing  characteristic  of  colloids 6 

Properties  of  silicic  acid 7 

The  properties  of  concentrated  clay  suspensions '8 

Ionic   reactions 1 /  8 

Effect    of    electrolytes 9 

Methods  of  Experimentation,  Materials  and  Apparatus 10 

Reagents 11 

Determination  of  the  hydrogen  ion  concentration 1 

Measurement  of  turbidity 1.. 

Experimental   Part    12 

Measurement  of  colloidal  substance 12 

The  influence  of  electrolytes  on  colloidal  silicic  acid 13 

Optimum   conditions   for  precipitation 17 

Influence  of  hydrogen  ion  concentration 20 

Coagulation  of  clay  suspensions 21 

The  effects  of  electrolytes  on  the  stability  of  clay  suspensions. ...  21 
The  effect  of  electrolytes  on  the  coagulation  of  clay  suspension 

by   aluminium   sulf ate 21 

The  influence  of  silicic  acid  in  the  coagulation  of  clay  suspension.  21 
Applications  to  the  Purification  of  Water 

Removal  of  silicic  acid 43 

The  coagulation  of  clay-bearing  surface  water 43 

Summary    . . ; 44 

References    ' 45 

Vita                                                                                                                                 .  47 


444300 


ILLUSTRATIONS. 


Comparison  between   the  pH,   the  precipitation   of   silicic   acid   and   the 

amount  of  A1(OH)3  in  the  solid  phase 19 

Comparison  between  the  pH  value,  the  precipitation  of  silicic  acid  and 

the  amount  of  A1(OH)3  in  the  solid  phase *. 19 

Effect  of  NaOH  on  the  coagulation  of  a  clay  suspension  by  A12(S04)3. . . .  26 
Comparison  of  A12(SO4)3,  colloidal  Fe,  Ca(OH)2,  Ba(OH)2  as  coagulants..  26 

Effect  of  H2SO4  on  the  coagulation  of  clay  suspensions  by  AL(SO4), 27 

Effect  of  electrolytes  on  the  coagulation  and  settling  of  clay  suspension. .   27 
Effect  of  electrolytes  on  the  coagulation  and  settling  of  clay  suspension. .   27 
Effect  of  the  addition  of  one  millequivalent  of  electrolytes  on  the  coagula- 
tion of  clay  suspension  by  A12(SO4)3 28 

Effect  of  Na2CO3  on  the  coagulation  of  clay  suspensions  by  A12(SO4)3 28 

Effect  of  NaHC03  on  the  coagulation  of  clay  suspension  by  AL(SO4)3 29 

Effect   of  Na2SO4   and   NaCl   on   the    coagulation    of   clay    suspension   by 

A12(SO4)3    30 

Effect  of  Mg(HCO3)2  and  of  CaCL  on  the  coagulation  of  clay  suspension 

by    AL(S04)8    31 

Effect  of  NaHCO3  on  the  coagulation  of  clay  suspension  by  A12(S04)3 -  32 

The    effect   of    Mg(HCO3)2    on    the    coagulation    of    clay    suspensions    by 

A12(S04)3    33 

The  effect  of  CaCl2  on  the  coagulation  of  clay  suspensions  by  A12(SO4)3. . .   34 
Effect  of  Ca(HCO3)2  on  the  coagulation  of  clay  suspension  by  A1,(SO4)3. . .   35 
Amount  of  aluminium  necessary  in  the  presence  of  silicic  acid  to  produce 
a  definite  clarification  and  effect  of  silicic  acid  on  coagulation  of  clay 

suspension  by  AL(S04)3 39 

The  effect  of  silicic  acid  on  the  coagulation  of  clay  suspensions  by  A12(S04)3  39 
Al  necessary  to  produce  a  definite  clarification  in  presence  of  silicic  acid. .  40 
The  effect  of  sodium  salts  on  the  coagulation  of  clay  suspension  by 

A12(S04)3  in  the  presence  of  silicic  acid 40 

Effect  of  silicic  acid  on  the  coagulation  of  clay  suspensions  in  the  presence 

of  electrolytes    ' v 41 

The    effect   of   silicic    acid    on    the   coagulation    of    clay    suspensions    by 

A12(S04)3 ; 42 

The   effect   of   silicic    acid    on    the   coagulation   of   clay    suspensions   by 
A12(S04)3    43 


SILICIC  ACID,  ITS  INFLUENCE  AND  REMOVAL  IN  WATER 

PURIFICATION. 

By  Otto  Mitchell  Smith. 


INTRODUCTION. 

Little  attention  has  been  paid  to  the  presence  of  silicic  acid  in 
natural  waters  except  in  cases  where  its  content  is  quite  high.  It  is  uni- 
versally present  but  usually  in  amounts  less  than  100  parts  per  million. 
It  is  more  prevalent  in  the  surface  waters  of  the  Mississippi  Valley16 
especially  on  the  western  watershed.  It  is  found  in  as  large  amounts  as 
1,163  parts  per  million  at  Cesenate,  Italy,46  1,230  parts  per  million  at 
Deep  Rock  Springs,  Oswego,  N.  Y.,13  and  923  parts  per  million  at  the 
Yellowstone  National  Park.37 

Silica  in  solution  usually  occurs  as  colloidal  silicic  acid  and32  in 
combination  with  the  basic  elements.  Its  presence  in  water  used  for 
steam  purposes  has  always  been  considered  detrimental  and  conducive 
to  the  formation  of  a  hard  flinty  scale.  Besides  forming  an  undesirable 
scale,  A.  Goldberg21  believes  silicic  acid  is  responsible  for  many  boiler 
disturbances.  When  the  acid  is  distilled  with  water  solutions  of  nitrates 
and  chlorides,  nitric  and  hydrochloric  acid  are  liberated. 

Turbidity  in  water  is  generally  caused  by  the  suspensions  of  very 
finely  divide^  mineral  matter,  mainly  clay.  Clay  may  be  defined  as  a 
mixture  of  minerals,  of  which  the  most  representative  members  are  the 
silicates  of  aluminium,  iron,  the  alkalies  and  alkaline  earths.  The 
hydrated  aluminium  silicate,  kaolin.  (Al203,2Si02,2H20)  is  the  most 
abundant  compound. 

There  are  many  cases  in  the  literature  emphasizing  the  difficulties 
of  clarifying  water  containing  finely  dispersed  clay  particles.  Fuller20 
in  1898  found  at  times  a  turbidity  which  was  difficult  to  coagulate  with 
an  abnormal  consumption  of  alum.  Ellms,17  Black  and  Veatch,7  and 
Catlett12  show  the  difficulties  in  the  treatment  of  such  water. 


THEORETICAL   AND    HISTORICAL    PART. 

As  silicic  Mcid  and  clay  suspension  are  considered  as  sol  and  suspen- 
soid  respectively  a  brief  discussion  of  the  general  properties  of  colloids 
is  pertinent.  Burton11  defines  a  colloid  solution  "as  a  suspension,  in  a 
liquid  medium,  of  fine  particles  which  may  be  graded  down  from  those 
of  microscopic  to  those  of  molecular  dimensions ;  these  particles  may  be 
either  homogeneous  matter,  solid  or  liquid,  or  solutions  of  a  small  per- 
centage of  the  medium  in  an  otherwise  homogeneous  complex.  The  one 
property  common  to  all  such  solutions  is  that  the  suspended  matter  will 
remain  almost  indefinitely  in  suspension  in  the  liquid,  generally  in  spite 
of  rather  wide  variations  in  temperature  and  pressure;  the  natural 
tendency  to  settle,  due  to  the  attraction  of  gravitation,  is  overbalanced 
by  some  other  force  tending  to  keep  the  small  masses  in  suspension." 

With  the  development  of  the  ultra  microscope  and  the  investigations 
of  Zsigmondy  and  Siedentopf53  it  is  possible  to  show  that  there  is  a  con- 
tinuous gradation  in  the  size  of  particles  of  the  disperse  phase  from 
1.70  x  10~7  cm.  in  diameter  to  that  of  visible  organisms  and  this  leads 
to  the  belief  that  there  is  a  gradation  in  size  from  the  smallest  of  these 
particles  to  the  molecules. 

Tyndall47  (1869)  found  that  smaH  particles  could  be  revealed  by 
the  lateral  diffusion  of  a  beam  of  light  traversing  a  solution.  Applying 
this  method  Linder  and  Picton29  were  able  to  grade  the  sizes  of  par- 
ticles of  colloidal  arsenous  sulfide. 

Wiedemann51  (1852)  and  Quincke39  (1861)  confirmed  the  discovery 
of  Reuss  that  a  liquid  would  move  across  a  diaphragm  or  through  a 
capillary  tube  towards  one  of  the  electrodes  when  a  current  is  passing. 
The  migration  of  sols  in  the  electric  field  was  first  observed  by  Linder 
and  Picton.  As  suspended  particles  carry  electrostatic  charges,  it  seems 
logical  to  conclude  that  as  result  of  these  charges,  suspended  particles 
whose  masses  are  small  enough  are  equally  distributed  throughout  the 
liquid,  and  prevented  from  ever  settling  because  of  the  mutual  repulsion 
of  the  charges.  Such  a  solution  is  called  a  sol  in  contradistinction  to 
the  jelly-like  form  called  a  gel.  When  the  dispersion  of  relatively  in- 
soluble particles  is  not  so  great  as  to  become  macroscopically  invisible — 
such  a  system  is  termed  a  suspension.  The  change  of  an  irreversible 
hydrosol  to  an  amorphous  precipitate  wherein  there  is  no  Brownian 
movement  is  known  as  coagulation. 

Schultz/3  and  Linder  and  Picton29  showed  that  the  coagulating 
power  depends  upon  the  valency  of  the  metal  ion  and  according  to  later 
workers,  equivalent  solutions  containing  monovalent,  bivalent  and  triva- 
lent  metallic  ions  would  possess,  whatever  the  nature  of  the  anion, 
coagulating  powers  in  the  ratio  of  1 :35 :1023  which  is  nearly  represented 


by  the  formulae  1  :x  :x2.  In  1899  Hardy22  found  that  the  concentration 
of  the  acid  necessary  for  coagulation  of  electronegative  particles  and  of 
alkali  for  the  coagulation  of  electropositive  particles  is  determined  by 
the  laws  of  ordinary  chemical  equilibrium. 

Burton/0  adding  graduated  amounts  of  aluminium  sulfate 
A12(S04)3  to  a  negative  sol,  found  that  there  was  a  decrease  and  even 
a  reversal  of  the  charge.  Thus  if  one  is  able  to  pass  from  a  negative 
sol  to  a  positive  sol  there  must  'be  a  point  of  zero  potential — "isoelectric 
point."  Hardy23  suggests  that  the  coagulation  of  colloids  by  electrolytes 
takes  place  when  the  particles  have  their  charges  neutralized  by  the 
adsorption  of  oppositely  charged  ions  of  an  electrolytic  solution  and  at 
the  isoelectric  point.  His  previously  published  conclusions  were24  that 
the  conditions  which  determine  coagulation  are:  (1)  concentration  of 
colloid,  (2)  temperature,  (3)  the  nature  of  the  ion,  and  (4)  that  the 
action  is  additive  if  the  ions  are  of  the  same  valency  and  "subtractive" 
if  of  different  valencies,  as  the  one  inhibits  the  other. 

Crum,  15  Linder  and  Picton, 29  and  Whitney  and  Ober,50  have  estab- 
lished the  fact  that  during  the  process  of  coagulation  a  portion  of  the 
electrolyte  is  always  adsorbed  by  the  coagulum  and  that  amount  is  pro- 
portional to  the  electrochemical  equivalents  of  the  anion. 

Lottermoser,28  Blitz,9  and  Billitzer5  demonstrated  that  colloids  of 
opposite  sign  precipitate  each  other;  that  there  is  an  optimum  of  pre- 
cipitating action  shown  for  certain  proportions  of  colloid  and  that,  if 
in  any  case  these  favorable  proportions  are  exceeded  on  either  side,  no 
precipitation  occurs ;  and  that  the  direction  of  migration  of  the  whole 
under  the  influence  of  the  electric  current  is  the  same  as  that  of  the 
colloid  in  excess.  This  leads  to  the  subject  of  protective  colloids.  Many 
organic  colloids  when  added  in  comparatively  minute  quantities  to 
suspensoids  have  the  power  of  preventing  the  coagulation  of  the  system. 

PROPERTIES  OF   SILICIC  ACID   AND  CLAY   SUSPENSIONS. 
Silicic  Acid. 

This  colloid  possesses  the  properties  common  to  its  class.  In  con- 
centrated solutions  it  is  unstable,  but  below  1  per  cent  it  is  stable  for 
years.  It  has  not  been  prepared  free  from  electrolytes;  its  molecular 
weight  is  about  49,000.  Billitzer4  and  Fleming19  found  it  amphoteric, 
carrying  a  negative  charge  in  akaline  and  a  positive  charge  in  acid  solu- 
tions. Fleming's  data,  converted  into  terms  of  hydrogen  ion  concentra- 
tion, indicate  that  the  isoelectric  point  lies  between  a  Ph  value  of  13.6 
and  13.9,  which  is  not  in  accordance  with  facts.  It  exhibits  the  Tyndal 
effect  and  is  precipitated  by  electrolytes  and  positive  colloids.  The 


8 

coagulation  from  dilute  solution  is  irreversible.  Hardy25  determined 
that  the  coagulating  power  of  electrolytes,  which  precipitate  a  solution 
of  about  1/120  normal  silicic  acid,  varies  with  the  cation,  the  anion 
having  little  effect.  Of  these  aluminium  sulfate  was  the  most  active  and 
sodium  salts  least.  It  is  also  coagulated  within  a  short  time  by  copper 
sulfate,  cadmium  nitrate,  calcium,  barium  and  strontium  chlorides  and 
carbonates,  barium  hydroxide,  concentrated  solutions  of  ammonium  sul- 
fate, dilute  solutions  of  egg  albumin,  glue,  basic  dyestuffs,  carbon  diox- 
ide gas  and  graphite. 

PapjJada35  found  that  neutral  salts  only  act  at  great  concentrations 
but  accelerate  gelation  (coagulation)  according  to  the  lyotope  series. 

S04  >  Cl  >  M)3;  and 
Ca  >  Kb  >  K  >  Na  >  Li 

Silicic  acid  hydrosols  do  not  act  as  a  protective  colloid  for  colloidal 
gold,  but  F.  Kuspert34  found  that  real  protective  action  occurs  at  the 
moment  the  silicic  acid  is  being  precipitated.  Silicic  acid  is  precipi- 
tated in  insoluble  compounds  by  many  chemical  reagents,  but  this  phase 
of  the  subject  is  not  here  discussed. 

Properties  of  Clay  Suspensions. 

Clay  suspensions  are  impure  suspensoids.  That  they  carry  a  nega- 
tive charge  is  shown  by  Ellms17  and  Count  Schwerin.44  Very  dilute 
suspensions  exhibit  the  Tyndal  effect.  Ultra-microscopic  observations 
have  shown  that  the  parties  probably  have  a  diameter  of  1.7  x  10~7 
cm.  or  less.  According  to  Mayer,  Schaffer  and  Terroine,80  the  addition 
of  a  trace  of  alkali  decreases  the  size  of  negative  suspended  particles. 
Ashley1  reviewing  the  work  of  many  investigators  came  to  the  conclusion 
that  the  colloids  in  clay  are  non-crystaline,  hydrated,  gelatinous  alum- 
inium silicates;  organic  colloids;  gelatinous  silicic  acid  and  hydrated 
ferric  oxide;  that  aluminium  hydrate,  A1(OH)3,  is  rarely  present;  and 
that  the  colloids  of  clay  may  carry  into  suspension  solid  particles  that 
are  wholly  non-colloidal,  according  to  the  ordinary  ideas,  which  particles 
may  stabilize  the  clay  sol.  The  work  of  Van  Bemmelen48  and  Parmelee36 
indicates  that  the  longer  clay  substance  is  washed  the  more  colloidal  it 
becomes;  and  that  bodies  are  gradually  hydrolyzed  from  crystaline 
compounds  to  soluble  colloids. 

Ionic  Reactions. 

A.  Lottermoser28  considers  that  "the  hydrosol  condition  is  only 
possible  if  one  of  the  reacting  ions  (I~  +  Ag+,  Fe+++  +  30H-,  Si02 
+  2H+)  remains  up  to  a  certain  minimum  amount  in  excess;  than  on 


exceeding  this  limit  the  gel  formation  begins  and  becomes  complete  if 
equivalent  amounts  of  the  reacting  ions  are  brought  together.  The  hy- 
drosol  condition  is  bound  up  with  the  presence  of  certain  ions  in  the 
colloid." 

If  sodium  carbonate  or  an  acid  be  added  to  a  clay  which  has  just 
enough  calcium,  Ca,  to  keep  the  colloid  matter  in  the  gel  form,  it  may 
react  according  to  the  following  equations: 

Ca  Gel  +  Na2C03  =  CaC03  +  Na2  Gel  or 
Ca  Gel  +  H2S04  =  CaS04  +  H2  Gel. 

Foerster18  first  perceived  the  nature  of  the  action  of  sodium  car- 
bonate on  the  clay  gel.  The  chemical  reactions  of  the  colloidal  matter 
in  clay  are  remarkably  similar  to  those  of  fats  and  soaps,  the  conditions 
of  solubility  and  insolubility  are  parallel,  but  the  colloidal  matter  of 
clay  is  more  readily  acted  upon.  Thus  in  a  general  way  the  salts  of  the 
fatty  acid  and  the  sodium,  and  ammonium  sols  of  clay  colloids  are 
soluble  in  water.  The  free  fatty  acid  and  the  acid  gels  are  insoluble  in 
water.  The  bivalent  and  trivalent  bases  form  insoluble  salts  with  soaps 
and  insoluble  gels  with  clays.  Ashley1  says  "The  proof  of  these  con- 
ceptions is  that  they  are  not  inconsistent  with  known  facts  about  clays ; 
that  they  have  proved  a  most  helpful  and  suggestive  guide  in  planning 
investigations,  and  that  they  have  never  misled/' 

Effect  of  Electrolytes  in  Clay  Suspensions. 

Much  valuable  information  is  available  in  the  ceramic  research  on 
the  action  of  salts  on  clay  suspensions.  The  effect  of  the  salt  varies  with 
(1)  the  clay;  (2)  its  previous  mechanical  treatment;  (3)  its  age;  (4) 
concentration;  (5)  degree  of  dispersion;  (6)  and  the  presence  of  col- 
loids. The  same  electrolyte  will  have  widely  different  effects,  coagulat- 
ing at  one  concentration  and  dispersing  at  another. 

The  work  on  slips  by  Eohland,40  Mellor  and  Green  and  Baugh,81 
Weber,49  Audley,3  Kerr  and  Fulton,83  Back,6  Ashley,2  Thomas,45  and 
Bleininger,8  shows  that  sodium,  potassium  and  lithium  hydroxides,  car- 
bonates, silicates  and  sulfides  generally  have  a  high  dispersive  or  stabil- 
izing power  while  the  most  active  coagulating  agencies 'are  the  salts 
of  bivalent  and  trivalent  metals.  In  Table  1  substances  have  been  classi- 
fied according  to  their  action  on  clay  slips: 


10 


TABLE  1 — ACTION  OF  VARIOUS  SUBSTANCES  ON  CLAY  SLIPS. 


Dispersing. 

Irregular. 

Neutral. 

Usually 
coagulating. 

Coagulating. 

Univalent  ions  in  the  presence  of 
high  hydroxyl  ion  concentra- 

NauSOs 
Na2SO4     - 

alcohol 
dilute 

Grape  sugar 
Humic  acid 

Bivalent  and  tri- 
valent    ions    in 

tion 

HgSO-4 

solutions  of 

Borax 

the  presence  of 

MgSO4 

NaCl 

NH4C1 

high  concentra- 

Alkali salts  of  weak  acids 

NaaPOV 

CaCl2 

tion  of  hydroxyl 

Na(C2HsO2) 

CaSO-4 

ions.    Bivalent 

Strongly  dissociated  salts  in  small 
concentration  (?) 

Ammonium 
gallate 

Ammonium  urate 
Aniline 

ions  in  the  pres- 
ence   of    mono 

NaCl 

Methyl  amine 

and    bivalent 

HC1 

Ethyl  amine 

ions 

K2SO4,  KHSO4,  KNOa 

Watei  glass 

Tannin 

Effect  is  to  make  the 

Gallic  acid 
Water  glass 

slip  thinner 
CuS04 

NH4OH 

Increasing     addition    tends    to 

K2S04A12(SO4)3.24 

coagulate  the  slip 

HiO 

Small  amounts 

"^ 

thicken  and  in- 

creasing amounts 

thin  the  slip 

- 

This  arrangement  seems  to  confirm  Hardy's  conclusions  that  the 
dispersion  or  coagulation  of  a  negative  sol  varies  inversely  with  the 
valency  of  the  cation,  and  that  the  action  of  anion  obeys  the  regular 
ionic  laws. 

The  above  data  are  obtained  from  concentrated  clay  suspensions 
where  the  ultimate  end  is  the  formation  of  a  stable  fluid  slip  of  the 
highest  clay  content.  In  water  purification  on  the  other  hand,  the  aim 
is  the  removal  of  a  very  small  amount  of  clay  from  a  large  amount  of 
water.  It  is  clearly  evident  from  a  study  of  dilute  clay  suspensions  and 
colloidal  silicic  acid,  that  the  physical  state  of  the  substances  and  their 
chemical  properties  must  be  taken  into  consideration,  together  with  the 
factors  which  influence  them,  i.  e.  (1)  degree  of  dispersion;  (2)  the 
presence  of  the  protective  colloids  and  absorbed  substances;  (3)  magni- 
tude and  kind  of  electric  charge;  (4)  the  liquid  or  dispersing  medium; 
(5)  the  ionic  content  of  the  liquid;  (6)  the  concentration;  (7)  the 
temperature,  and  (8)  the  speed  of  reaction  of  added  substances. 

METHODS     OF     EXPERIMENTATION,     MATERIAL     AND     APPARATUS. 

Briefly,  the  experimental  work  has  developed  along  three  lines: 
(1)  the  removal  of  silicic  acid  from  solutions  by  electrolytes  and  col- 
loids; (2)  the  effect  of  electrolytes  on  dilute  clay  suspensions,  and  (3) 
the  effect  of  silicic  acid  on  the  coagulation  of  clay  suspensions  by  alum 
in  the  presence  of  electrolytes. 


11 

Regeants. 

Washed  potters'  clays  were  used  in  making  the  suspensions.  No 
attempt  was  made  to  obtain  the  clay  in  a  high  state  of  purity.  Those 
clays  which  remained  in  longest  suspension  were  Tennessee  Ball  Nos. 
3  and  1,  number  three  being  the  best.  Ashley1  rates  Tennessee  No.  3 
as  having  a  relative  colloid  content  of  95  to  100  per  cent.  The  clay 
was  freed  from  large  particles  and  soluble  salts  by  washing  with  distilled 
water  and  running  the  suspension  through  a  Sharpies  super-centrifuge ; 
the  desired  end  was  a  suspension  nearly  like  that  in  surface  waters  but 
as  free  as  possible  from  electrolytes. 

Characterization  of  Suspensions. 

Coefficient  of 

By  turbidimeter.     By  weight,     fineness. 

Tennessee  No.  1  Ball    '  400*  325*  0.75 

Tennessee  No.  3  Ball  400  330  0.82 

The  No.  3  clay  stood  in  contact  with  water  in  ordinary  glass  bottles 
over  one  year  before  being  used.  Kahlbaum's,  Merck's,  or  analyzed 
chemicals  were  used  without  further  purification.  Colloidal  silicic  acid 
was  prepared  as  directed  by  Graham  and  dialyzed  with  parchment  paper 
until  there  remained  only  a  trace  of  chloride.  Determination  of  hydro- 
gen ion  concentrations  was  by  the  colorimetric  method  of  Clark  and 
Lubs.14  Standards  and  indicators  were  made  as  directed  using  ordinary 
distilled  water.  The  accuracy  of  the  solutions  was  determined  by  check- 
ing against  fresh  permanent  standards  prepared  by  Clark  and  Lubs. 
The  accuracy  of  the  readings  is  within  -f-  0-1  P^  value. 

Measurements   of  Turbidity. 

Standards  for  determining  turbidities  were  prepared  from  the 
original  clay  suspensions  and  checked  with  a  standardized  turbidimeter. 
Turbidities  were  not  read  closer  than  7  per  cent.  Fine  particles  of 
various  sizes  in  suspension  do  not  settle  uniformly  leaving  a  clear 
supernant  liquid  but  are  deposited  in  layers  or  zones.  According  to 
Wiley's  formulae,  which  is  determined  for  particles  between  0.0001 
and  0.02  millimeters  in  diameter,  the  rate  of  fall  is  proportional  to  the 
square  root  of  the  diameter  of  the  particle  that  is  D  =  0.0255V.2 

Those  particles  of  approximately  the  same  diameter  will  settle  to- 
gether leaving  a  turbid  suspension  of  finer  particles  above.  In  a  sus- 
pension one  can  observe  two  or  three  of  these  zones  of  widely  different 
turbidities  and  rates  of  sedimentation.  Within  a  zone  the  turbidity  is 

*  Expressed  in  parts  per  million. 


12 

fairly  uniform,  but  different  zones  vary  as  much  as  100  per  cent  within 
a  vertical  distance  of  %  inch. 

If  the  turbidity  of  an  undisturbed  suspension  be  taken  at  regular 
intervals  at  a  fixed  point,  it  will  be  noticed  that  the  numerical  values 
will  be  nearly  constant  for  some  time,  then  within  a  brief  interval  of 
time  will  change  markedly  as  particles  from  a  higher  zone  traverse  the 
field  of  view.  This  phenomenon  is  well  shown  in  many  of  the  figures. 
As  it  was  necessary  to  determine  the  turbidity  of  a  suspension  Without 
disturbing  the  liquid,  the  following  method  was  devised.  A  stereopticon 
equipped  with  a  500  watt  lamp  was  adjusted  to  yield  a  slightly  diverging 
cone  of  light.  Two  screens  each  having  four  holes  3/16  inches  in 
diameter  were  inserted  in  the  path  of  this  beam.  The  holes  in  each 
screen  were  in  a  vertical  row  arranged  in  pairs.  The  centers  of  the  holes 
were  %,  %,  and  2%  inches  below  the  surface  of  the  liquid  in  the  sample 
bottles.  One  screen  was  placed  l1/^  inches  in  front  of  and  iy2  inches 
to  the  side  of  the  other  screen  so  that  the  standard  and  the  unknown 
could  be  observed  together.  The  observations  were  made  at  right  angles 
to  the  beam  of  light. 

The  100  cc.  samples  were  contained  in  4-ounce  French  square  flint 
bottles,  1%  inches  square;  the  depth  of  the  liquid  was  2%  inches.  For 
turbidities  below  100  parts  per  million  the  ordinary  method  of  compar- 
ing with  standards  in  similar  bottles  was  used.  In  the  coagulation  of 
the  suspensions,  the  reagents  were  added  in  sufficient  concentrations  to 
give  a  reaction  before  the  natural  occurrence  of  sedimentation  of  par- 
ticles. 

All  results  are  expressed  as  turbidities  in  parts  per  million,  and 
milligram  equivalents  per  liter,  except  in  the  case  of  colloidal  silicic 
acid  which  is  in  parts  of  Si02  per  million. 

EXPERIMENTAL  PART. 

In  dealing  with  the  action  of  electrolytes  on  colloids  a  method  of 
determining  the  amount  of  colloids  present  is  greatly  "to  be  desired.  A 
search  of  the  literature  revealed  only  one  method  that  seemed  applicable. 
This  was  devised  by  Eohland41  and  improved  upon  by  Ashley.1  It  de- 
pends upon  the  amount  of  dye  adsorbed  by  the  colloid  and  is  fairly 
successful  in  estimating  the  adsorptive  or  colloidal  power  of  concentrated 
clay  suspension,  but  is  not  reliable  when  applied  to  dilute  suspensions 
of  clay.  Further  work  along  this  line  is  needed.  The  refractive  index 
and  viscosity  were  investigated,  but  variations  were  too  slight  to  be 
serviceable.  There  appeared  to  be  no  correlation  between  the  hydrogen 
ion  concentration  and  the  degree  of  coagulation.  Kataphoresis  experi- 
ments only  measure  the  sign  and  not  the  magnitude  of  the  charge. 


13 


Later  in  the  work  it  was  found  that  silicic  acid  exerted  a  marked  in- 
fluence and  an  endeavor  was  made  to  find  a  method  of  separating  it 
from  the  clay.  Several38'52  have  been  given  but  none  of  sufficient  selec- 
tive action  to  be  of  value  at  these  dilutions. 

An  attempt  was  made  to  filter  the  silicic  acid  from  a  suspension  by 
a  Berkefeld  army  filter  No.  3  with  the  following  results: 

Silicic  Acid. 

added.  recovered. 

298*  155 

129  84 

This  confirms  the  work  of  Linder  and  Picton.29  The  silicic  acid 
is  evidently  coagulated  by  contact  with  the  walls  of  the  filter. 

INFLUENCE  OF  ELECTROLYTES  ON  THE  PRECIPITATION  OF  SILICIC 
ACID  FROM   DILUTE  SOLUTIONS. 

The  amount  of  colloidal  silicic  acid  in  a  solution  containing  no 
suspensoids  is  easily  obtained  by  the  usual  method  of  analysis.  In  the 
determinations  of  silica,  Si02,  one  evaporation  was  made,  as  on  a  second 
evaporation  only  a  few  tenths  of  a  milligram  additional  was  obtained.27 
The  errors  due  to  the  manner  of  adding  the  reagents  and  their  different 
concentration  was  reduced  to  a  minimum  by  making  the  methods  of 
manipulation  as  uniform  as  possible. 

TABLE  2 — SILICIC  ACID  is  NOT  PRECIPITATED  FROM  5  cc.  OF  A  SOLUTION- 
CONTAINING  625  PARTS  PER  MILLION  Si02  BY  THE  FOLLOWING 
SALTS  I 


Reagent. 

Temperature  ca 
23°  C. 

Reagent. 

Time  6  hours. 

No.  cc. 
used. 

Highest 
concen- 
tration. 

No.  cc. 
used. 

Highest 
concen- 
tration. 

0  1  N  NaCl 

12 
12 
12 
12 
8 
12 
12 

.07N 
.07N 
.07N 
.07N 
.06N 
.07N 
.07N 

0  2  N  BaCb 

8 
4.2 
12 
11 
12 
10 
12 

.06N 
.05N 
.07N 
.07N 
,07N 
.07N 
.07N 

0  1  N  Na2COs 

1.0  N  CaCl2 

0  1  N  NaHCOs 

0  5  N  Ah(SO4)3 

0.1  N  Na2S04  andK2SO4  
0  1  N  NasPO4 

0.1  N  Feds... 

0.1  N  FeSO4(NH4)2SO4 

0.1  N  Mg(HCO3)2 

0.1  N  FeCl2... 

0.  1  N  MgSO4 

0.  1  N  Aids 

From  a  solution  containing  not  less  than  184  nor  more  than  625 
parts  per  million  of  Si02,  silicic  acid  is  not  precipitated  by  the  reagents 
given  in  Table  1,  but  is  precipitated  from  5  cc.  of  a  solution  containing 
625  parts  per  million  of  Si02,  by  the  following : 


*  Expressed   as   parts    per   million. 


14 


Temperature  ca  23 °C.  Time:  5  minutes. 

5-5  cc.    0.18  N"        NaOH  .099     N  concentration 

•6  cc 0.018  N       Ca(OH)2         .0019  N  concentration 

•4  cc 0.26  N        Ba(OH)2         .0019  N  concentration 

2-6  cc (.6  mg)  colloidal  Fe         .0045  N  concentration 

This  experiment  indicates  that  bivalent  ions  have  a  precipitating 
value  fifty  times  that  of  monovalent  ions.  Trivalent  ions  according  to 
the  formulae  l:x;  x2  should  have  a  coagulating  value  of  2,500  times 
that  of  the  univalent,  or  fifty  times  that  of  the  bivalent  ions.  Qualitative 
experiments  with  more  dilute  solutions  indicate  that  the  ratio  between 
bivalent  and  trivalent  to  be  about  one  to  four.  Colloidal  iron  is  only 
one-half  as  efficient  as  calcium  hydroxide.  The  more  dilute  a  solution 
the  less  marked  is  this  precipitating  effect  of  the  cations. 

Very  dilute  solutions  — 30  or  40  parts  per  million  of  Si02 — are  not 
precipitated  by  sodium  hydroxide,  and  rather  high  concentration  of 
calcium  hydroxide  to  silicic  acid  are  necessary  to  obtain  a  precipitate 
within  six  hours.  At  these  concentrations  the  reactions  no  doubt  are 
ionic,  and  precipitates  of  calcium  silicates  are  thrown  down.  Since  the 
hydroxides  of  calcium  and  barium  precipitate  silicic  acid,  it  is  desirable 
to  know  the  effect  of  added  univalent  and  bivalent  ions  upon  the  amount 
of  calcium  hydroxide  needed. 

To  5  cc.  of  a  dialyzed  silicic  acid  solution,  containing  625  parts 
per  million  of  Si02  there  was  added  0.5  cc.  of  a  0.1  normal  solution  of 
the  electrolytes  and  the  silicic  acid  was  precipitated  by  the  addition  of 
calcium  hydroxide.  The  results  are  given  in  Table  3. 

TABLE  3 — THE  EFFECT  OF  THE  ADDITION  OF  VARIOUS  ELECTROLYTES  ON 

THE     PRECIPITATION     OF     COLLOIDAL     SILICIC     ACID*     BY     CALCIUM 
HYDROXIDE. 


Temperature  ca  23°C. 

Time  5  minutes. 

Reagent. 

Ca(OH)2  required. 

0.0  cc. 

0.2  N 

Ca(OH)2 

0.  6  cc. 

0.5  cc. 

0.1  N 

BaCl2 

0.3  cc. 

0.5  cc. 

0.1  N 

MgSO4 

0.3  cc. 

0.5  cc. 

0.1  N 

CfcCb 

0.3  cc. 

0.  5  cc. 

0.1  N 

NaHSO4 

0.3  cc.  1  in  excess  re- 

0.5  cc. 

0.1  N 

H2SO4 

0.  35      [quired  to 

0.5  cc. 

0.1  N 

KHSO4 

0.  3  cc.  J  neutralize 

0.5  cc. 

0.1  N 

NaCl 

0.6  cc. 

0.5  cc. 

0.1  N 

Na2SO4 

0.  7  cc. 

0.5  cc. 

0.1  N 

K2SO4 

0.7  cc. 

0.5  cc. 

0.1  N 

Na2SO4 

0.  6-0.  7  cc. 

*  5  cc.  of  silicic  acid  containing  625  parts  per  million  of  SiO2  were  used. 


15 

The  following  compounds  complicate  the  precipitation  by  reacting 
with  the  Ca.  ions:  V, 

Na2C03  Na3P04  Ca(HC03)2 

NaHC03  Mg(HC02)3 

This  experiment  proved,  as  expected,  that  the  precipitating  value 
of  the  cation  depends  upon  its  valence  and  that  hydroxyl  had  some  in- 
fluence at  these  concentrations.  Neutral  salts  of  the  univalent  cations 
were  not  present  in  sufficient  amount  to  influence  the  results.  In  cases 
where  the  solution  was  acid  or  there  was  formed  an  insoluble  calcium 
precipitate,  the  concentration  of  calcium  ion  is  that  necessary  to  com- 
bine with  the  anion  plus  an  amount  sufficient  to  produce  precipitation. 
This  is  shown  in  the  reactions  of  sulfuric  acid  and  calcium  hydroxide. 

To  measure  the  effect  of  the  hydroxylion  on  the  reaction,  the  pH 
value  was  determined,  the  results  of  which  are  given  in  Table  4. 

TABLE  4 — THE  CONCENTRATION  OF  HYDROGEN  ION  NECESSARY  BEFORE 
SILICIC  ACID*  IS  PRECIPITATED  BY  Ca(OH)2  IN  THE  PRESENCE  OF 

SALTS. 

Salts.  pH  value. 

0.18  N  NaOH 9.5 

0.01    N   Ca(OH)2....' 9.2 

0.02  N  NaOH 9.2 

colloidal  Fe off  color 

Precipitation  of  silicic  acid  by  Ca(OH)2  in  presence  of  0.5  cc.  of 
0.1  normal  salt  solutions : 

Salts.  pH  value. 

0.1  N  CaCl2...: -. .   9.2 

0.1  N  MgS04 8.6 

0.1  N  H2S04 9.2 

0.1   N   NaCl 9.3 

0.1  N  NaHS04 9.0 

0.1  N  NaHC03 9.2 

0.1  N  Na,S04 9.4 

0.1  N  Na2C03 9.4 

0.1  N  Na3P04 9.3 

10  cc.  CaS04  saturated  soln . 9.2 

0.1  N  Mg(HC03)2 8.8 

0.1  N  MgS04 8.6 

0.1   N  A1C13. below  7.5  when  precipitation  occurred 

0.1  N  A12(S04)3 .below  7.5  when  precipitation  occurred 

Average    9.0 

•  5  cc.  of  a  solution  containing  625  parts  per  million  of  SiO2  were  used. 


16 


The  different  systems  of  salt,  silicic  acid  and  calcium  ions  have 
different  normalities  but  approximately  a  pH  value  of  9.0.  This  points 
to  the  fact  that  silicic  acid  may  act  as  a  buffer  in  the  manner  of  large 
complex  organic  molecules.  Magnesium  salts  show  a  lower  value  than 
calcium  which  is  probably  due  to  the  precipitation  of  magnesium  hydrox- 
ide which  obscured  the  true  end  point.  It  was  not  possible  to  determine 
hydrogen  ion  concentration  of  iron  salts  with  indicators.  The  quanti- 
tative removal  of  silicic  acid  by  calcium  hydroxide,  barium  hydroxide 
and  chloride,  aluminium  sulfate  and  colloidal  iron  was  tried  on  a  water 
from  Albuquerque,  N.  M.,  the  analysis  of  which  is  given  in  Table  5. 

TABLE  5— ANALYSIS  OF  SAMPLES  OF  WATER  FROM  ALBUQUERQUE, 

NEW   MEXICO. 


Residue.* 

479.1  p.  p.  m. 

N 
equivalents 
1000 

Silica 

SiO2 

82.6 

Non  volatile.  

0.3 

AhOs  Fe2<D3 

0.2 

Iron  

Fe 

.03 

Manganese  . 

Mn 

0 

Calcium 

Ca 

69.6 

3.473 

Magnesium  .  

Mg... 

14.0 

1.145 

Sodium  and  potassium 

Na  &  K 

76.8 

3.257  sum  7.875 

Ammonia  

NHs 

0.06 

COa 

84 

2  800 

Sulfate... 

SO4 

175.3 

3.647 

Chloride  

Cl 

46.5 

1.311 

Nitrate 

NOs 

1.6 

.026  sum  7.784 

Nitrite  

NO2 

0.0 

Difference  .091 

Phosphate 

P2O5 

0.  0   Error 

of  analysis  -0.58  per  cent. 

*  NOTE. — Owing   to   reaction   between   fixed   alkalies   and   silica   on   evaporation 
and  heating,  the  residue  is  too  low.         •;.'. 

The  reagents  were  added  in  excess  (but  the  amount  of  this  excess  unfor- 
tunately was  not  recorded)  and  the  reaction  carried  out  at  a  pH  value 
of  8.5  to  10.  Five  different  treatments  were  tried.  The  amount  of 
calcium  and  barium  compounds  were  those  necessary  for  softening  and 
removing  sulfates. 

1.  Ca(OH)2  and  heating  to  90 °C.  removed  37  per  cent  leaving  52 

ppm.  in  soln. 

Ba(OH)2  and  heating  to  8-0°C.  removed  36  per  cent  leaving  53 
ppm.  in  soln. 

2.  Ca(OH)2,  filtration  and  adding 

A12(S04)3  removed  30  per  cent  leaving  58  ppm.  in  soln. 
A1C13  +  NaOH  removed  84  per  cent  leaving  13  ppm.  in 

soln. 
FeS04(NH4)2S04  removed  37  per  cent  leaving  51  ppm. 

in  soln. 


17 

3.  Ca(OH)2,  Ba(OH)2,  BaCl2,  filtration  and  adding 

colloidal  Fe  removed  38  per  cent  leaving  31.6  ppm.  in  soln. 
excess  Ba(OH)2  removed  44  per  cent  leaving  36.0  ppm. 

in  soln. 
A1C13  +  NaOH  removed  91  per  cent  leaving  5.0  ppm. 

in  soln. 

4.  A12(S04)3  and  Ca(OH)2  removed  34  per  cent  leaving  55  ppm, 

in  soln. 

5.  Treatment  with  colloidal  Fe  removed  26  per  cent  leaving  61 

ppm.  in  soln. 

A1(OH)3  cream  removed  44.6  per  cent  leaving  38  ppm. 
in  soln. 

It  is  evident  that  the  most  efficient  precipitants  are  the  trivalent 
ions  in  an  excess  of  hydroxyl  ions.  According  to  the  theory  of  coagula- 
tion, the  optimum  conditions  for  precipitation  of  negatively  charged 
silicic  acid  should  be  (1)  an  amount  of  trivalent  cations  or  positively 
charged  colloids  to  exactly  neutralize  the  negative  charges,  (2)  a  mini- 
mum amount  of  cations,  protective  or  stabilizing  colloids,  and  (3)  a  pH 
value  approaching  the  isoelectric  point.  Just  what  conditions  must  be 
defined  in  order  to  locate  the .  isoelectric  point,  chemists  have  not  yet 
discovered.  Fleming19  designated  it  in  terms  of  normality  of  the  solu- 
tion, but  it  seems  preferable  to  express  it  as  hydrogen  ion  concentration. 

The  above  tests  indicate  that  the  optimum  pH  value  for  the  pre- 
cipitation of  silicic  acid  is  approximately  9.0.  According  to  theory  this 
should  be  the  location  of  the  isoelectric. point.  In  order  to  determine 
this  value  more  accurately  and  in  the  absence  of  bivalent  cation,  alumi- 
nium hydroxide  was  precipitated  in  the  silicic  acid  solution  by  sodium 
hydroxide  and  aluminium  chloride. 

The  silicic  acid  used  was  prepared  by  bringing  a  solution  of  sodium 
silicate  to  a  pH  value  of  6.5  by  the  addition  of  hydrochloric  acid.  This 
solution  contained  4  mols  of  Si02  to  one  mol  of  NaCl.  Two  dilutions 
were  used:  87  and  232  parts  per  million  of  Si02.  To  the  silicic  acid 
solution  were  added  water  to  produce  the  proper  dilution,  aluminium 
cloride  and  N/10  sodium  hydroxide,  which  was  added  drop  by  drop  with 
constant  shaking.  These  solutions  were  shaken  at  frequent  intervals 
during  48  hours.  By  that  time  the  reaction  was  practically  complete. 
The  solution  was  filtered  and  silicic  acid  determined  in  the  filtrate.  It 
was  noticed  in  precipitating  aluminium  from  a  solution  of  aluminium 
chloride,  silicic  acid  and  sodium  chloride,  that  the  manner  of  adding 
'the  reagents  and  the  relative  ratio  of  aluminium  to  silicic  acid  markedly 
influenced  the  character  and  amount  of  the  precipitate.  Table  6  shows 
tin's  very  strikingly. 


18 


TABLE  C — RELATIONSHIP  BETWEEN  THE  AMOUNT  OF  SILICIC  ACID  PRE- 
CIPITATED AND  THE  CHARACTER  OF  THE  PRECIPITATE. 

SiO2 — Content  87  parts  per  million — Temp,  ca  23°C — Time  48  hrs. 


Milliequivalents 
of  Al. 

SiOa  p.  p.  m. 
precipitated. 

SiO-2  p-  p.  m. 
in  Soln. 

pH 

Remarks. 

1.75 

8 

79 

7.1 

Faint  turbidity. 

1.75 

3 

84 

7.5 

Clear. 

2.91 
2.91 

2 
4 

85 
83 

7.5 
7.5 

Faint  turbidity. 
Faint  turbidity. 

4.37 

5.87 

51 

65 

36 
22 

6.8 
7.0 

Fair  precipitate. 
Well  nocked. 

5.87 
7.28 

35 
75 

52 
12 

7.6 
7.0 

Faint  turbidity  opalescent  nitrate. 
Well  nocked. 

7.28 

45 

42 

7.6 

Tuibid. 

8.73 

80 

7 

7.1 

Well  nocked. 

8.73 

81 

6 

7.6 

Well  flocked. 

Poor  removal  of  silicic  acid  is  associated  with  a  turbid  colloidal 
solution  and  a  sticky  gelatinous  precipitate  which  is  very  difficult  to 
filter,  while  a  good  removal  is  usually  obtained  when  the  precipitate  is 
well  fioculated  and  settles  quickly;  the  resulting  clear  solution  exhibits 
little  Tyndal  effect.  In  the  absence  Q£  silicic  acid  a  flocculent  precipitate 
of  aluminium  hydroxide  was  produced  in  a  dilute  solution  of  A1CL  by 
N/10  NaOH,  or  in  a -dilute  solution  of  Na(OH)  by  0.0003N"  A1C18,  re- 
gardless of  the  manner  of  adding  reagent,  or  presence  of  NaCl.  If  the 
above  solution  contained  87  parts  per  million  of  Si02,  as  colloidal  silicic 
acid,  on  adding  N/10  NaOH  drop  by  drop,  a  precipitate  formed  at  the 
end  of  one  hour  depending  upon  the  amount  of  A1C13  in  the  solution,  but 
if  an  equivalent  amount  of  NY10  or  stronger  NaOH  was  added  all  at 
once,  no  precipitate  formed.  Such  a  solution  showed  a  very  strong 
Tyndal  effect  and  gradually  deposited  a  slight  fine  precipitate.  One 
solution  was  made  from  which  a  very  little  precipitate  settled  at  the 
end  of  a  month.  Apparently  the  system  was  less  stable  the  higher  the 
concentration  of  NaOH  and  the  more  suddenly  it  was  added  and  mixed. 
The  same  effect  was  produced  when  sodium  carbonate  or  acid  carbonate 
was  used  instead  of  hydroxide. 

With  calcium  hydroxide  an  excellent  precipitate  formed  regardless 
of  the  manner  of  adding  the  reagent.  There  is  evidently  some  complex 
substances  formed  under  these  conditions,  which  are  intimately  con- 
nected with  a  sodium  ion  and  the  silicic  acid.  Perhaps  the  silicic  acid, 
in  the  presence  of  sodium  ions,  is  acting  as  a  protecting  colloid  pre- 
venting in  some  manner  passage  of  aluminium  hydroxide  from  the 
colloid  into  the  crystaline  condition.  In  any  event,  a  recognition  of  this 
fact  is  quite  valuable  in  obtaining  well  flocked  precipitates. 

A  high  ratio  of  silicic  acid  to  aluminium  tends  to  produce  colloidal 
solutions  while  the  reverse  ratio  produces  nicely  flocked  precipitates. 


19 

The  magnitude  of  the  Tyndal  effect  is  inversely  related  to  the  removal 
of  the  silicic  acid  and  the  character  of  the  flock  or  precipitate. 

Thus  in  plotting  the  curves,  Figures  1  and  2,  from  Tables  7  and  8 
respectively,  only  the  higher  concentrations  of  aluminium  were  used. 


80 


& 


20 


3.7  MILLlEQVIVALENrS   Of  ALUMINUM 


\ 

SiO  MILL!  EQUIVALENTS 
OF   ALUMINUM 


pH  Value. 

Figure  1. — Comparison  between  the  pH  value,  the  precipitation  of  silicic  acid  and 
the  amount  of  A1(OH)3  in  the  solid  phase. 


•  UO///IU/  J9C/  SfJDC/  Ul  *()!£ 

. 

-zoo 

^~ 

£$& 

/ 

s' 

& 

4* 

150 

• 

* 

/ 

"c 

Take 
vmtr 

n  fro 
>um 

m  a 
valm 

cons* 
vof 

tent 
/&. 

3 

0 

W 

7 

2k 

A/ 

100 

/° 

7 

X 

-?nn 

:/ 

2 

? 

c^ 

/ 

\ 

5 

-50 

/ 

/W 

( 

5      7     t 
PH  V< 

\ 

J      £ 

i/ue 

>     / 

I 

0    4 

0     6. 

0     <J 

0     /i 

W     /t 

?.     l< 

(     / 

5.     A 

9.     £ 

I 

Milliequivalents  of  Aluminium. 

Figure  2. — Comparison  between  the  pH  value,  the  precipitation  of  silicic  acid,  and 
the  amount  of  Al(OH),  in  the  solid  phase. 

The  lower  values  are  inaccurate  because  of  the  formation  of  colloidal 

% 

solutions.  There  is  shown  in  Figure  1  a  third  curve  plotted  from  the 
data  in  Table  9.  Values  for  this  curve  were  obtained  by  precipitating 
the  aluminium  with  ammonia  in  the  absence  of  silicic  acid. 


TABLE  7 — BEMOVAL  OF  SILICIC  ACID*  BY  ALUMINIUM  HYDEOXIDE  OP, 
VARYING  HYDROGEN  ION  CONCENTRATION. 


Temperature  ca  23°C. 

Time  48  hours. 

Milliequivalents  of  Al. 

SiOa  precipitated. 

SiO2  in  solution. 

pH 

8.73 

73 

14 

6.8 

8.73 

79 

8 

7.5 

8.73 

79 

8 

8.0 

8.73 

74 

13 

9.6 

8.73 
5.82 

0 
9 

87 
78 

11.     no  ppt. 
5.2  colloidal. 

5.82 

63 

24 

7.5 

5.82 

65 

22 

8.2  colloidal. 

5.82 

38 

49 

9.5 

*  Concentration  of  SiO2  is  87  parts  per  million. 

TABLE  8 — PRECIPITATION  OF  SILICIC  ACID  IN  SOLUTIONS  OF  VARYING 

HYDROGEN  ION  CONCENTRATION  BY  Al  (OH)3. 

Concentration  of  SiO, — 232  parts  per  million 
Temperature  ca  23 °C.     Time  48  hours. 


Milli-equivalents 
of  Al. 

Parts  per  millions. 

Remarks. 

Si02 
precipitated. 

SiO2 
in  solution. 

pH 

value. 

1.94 

50 

182 

4.7 

Slight  turbidity. 

9.70 
17.5 

4.4 
4.4. 

No  precipitate. 
No  precipitate. 

, 

1.94 

6.0 

Slight  turbidity. 

5.82 
9.70 

98 
149 

134 
83 

5.9 
6.0 

Slight  turbidity. 
Slight  turbidity. 

11.70 
1.94 

220 
4 

12 

228 

6.1 

6.7 

Precipitated. 
Slight  turbidity. 

4.03 

26 

206 

7.0 

Turbid. 

5.82 

96 

136 

6.7 

Difficult  to  filter. 

7.76 
9.70 

120 
142 

112 
90 

6.4 
6.5 

Well  precipitated. 
Well  precipitated. 

11.70 

167 

65 

6.6 

Difficult  to  filter. 

13.60 

173 

59 

6.7 

Difficult  to  filter. 

15.50 

172 

60 

6.8 

Difficult  to  filter. 

17.50 

191 

41 

6.9 

Difficult  to  filter. 

19.40 

208 

24 

7.2 

Difficult  to  filter. 

3.0 

17 

215 

9.8 

Tendency  to  be  colloidal.    Filtered 

through    Blue    Ribbon    No.    589 

Filters. 

3.7 

21 

211 

8.8 

do. 

4.4 

5 

9.2 

do. 

5.9 

57 

175 

8.7 

do. 

6.7 

101 

131 

8.7 

do. 

7.4 

101 

131 

8.6 

do. 

8.1 

37 

195 

8.8 

do. 

9.2 

73 

159 

8.5 

do. 

11.1 

87 

145 

8.6 

do. 

14.8 

167 

65 

8.8 

Well  flocked. 

'        20.6 

220 

12 

8.9 

Well  flocked. 

.74 

3 

229 

7.2 

Settles  well. 

1.5 

47 

185 

7.8 

Well  flocked. 

2.2 

61 

171 

7.8 

Well  flocked. 

3  0 

59 

173 

7.0 

Well  flocked. 

3.7 

81 

151 

8.0 

Well  flocked. 

4.4 

79 

153 

8.0 

Well  flocked. 

5  2 

95 

137 

7.4 

Well  flocked. 

5.9 

99 

133 

7.6 

Well  flocked. 

6.7 

99 

133 

7.6 

Well  flocked. 

7.4 

129 

103 

8.4 

Well  flocked. 

9.2 

159 

73 

7.4 

Well  flocked. 

11.1 

167 

65 

8.6 

Well  flocked. 

13.0 

197 

35 

8.6 

Well  flocked. 

14.8 

209 

23 

8.2 

Well  flocked. 

18.5 

197 

35 

7.6 

Well  flocked. 

21 

TABLE  9 — EFFECT  OF  THE  HYDROGEN  ION  CONCENTRATION   ON  THE 
PRECIPITATION  OF  ALUMINIUM  HYDROXIDE. 


Temperature  ca.  28  *C. 

Time  48  hours. 

Ph  value 

6.8 
1.5* 
good 

8.0 
0.5 
good 

6.8 
12 
good 

9.4 
17.3 
gelationous 

Al  in  solution  

Character  of  flock  

*  Expressed  as  parts  per  million. 

A  study  of  data  and  curves  indicates:  (1)  that  silicic  acid  is  best 
precipitated  at  a  pH  value  of  8.0  to  8.5,  which  is  probably  a  closer 
approximation  to  the  truth  than  the  former  value  of  9.0  obtained  with 
calcium  hydroxide,  (2)  that  the  amount  of  silicic  acid  precipitated  fol- 
lows closely  'the  amount  of  aluminium  hydroxide  in  the  solid  phase,  and 
(3)  that  below  a  pH  value  of  4.0  the  concentration  of  the  hydrogen  ion 
shifts  the  reaction  so  far  to  the  right  in  the  equation. 

H+  +  A102-  +  H20  *=*  A1(OH)3  ±=>  A10+  +  HO  +  H20 
and  that  above  a  pH  value  of  11.0  so  far  to  the  left  that  the  solid 
aluminium  hydroxide  phase  is  unstable  and  disappears. 

In  the  region  below  these  curves  the  tendency  to  form  colloidal 
solutions  is  quite  marked,  and  the  gelatinous  nature  of  the  precipitate 
and  the  magnitude  of  the  Tyndal  effect  generally  varies  inversely  with 
the  amount  of  aluminium  ions  added  to  the  system,  and  directly  as  the 
hydrogen  ion  concentration  departs  in  either  direction  from  a  pH  value 
of  8.25. 

The  precipitation  of  silicic  acid  by  aluminium  sulfate  may  be  ex- 
plained :  ( 1 )  by  the  neutralization  of  the  charge  on  the  silicic  acid  com- 
plex by  the  aluminium  ion,  resulting  in  a  precipitation  of  silicic  acid, 
(2)  by  the  neutralization  of  the  negatively  charged  silicic  acid  by  posi- 
tively charged  aluminium  hydroxide,  (3)  by  the  solid  aluminium  hy- 
droxide adsorbing  silicic  acid,  and  (4)  by  the  formation  of  an  insoluble 
chemical  compound. 

THE    INFLUENCE    OF    ELECTROLYTES    AND    SILICIC    ACID    ON    THE 
COAGULATION  OF  CLAY  SUSPENSIONS. 

Jhe  next  step  was  to  determine  the  effect  of  silicic  acid  and  the 
commonly  occurring  electrolytes  on  the  coagulation  of  a  clay  suspension 
with  aluminium  sulfate. 

Reagents  were  added  to  one  hundred  cubic  centimeter  portions  of 
a  clay  suspension  and  thoroughly  mixed  by  shaking  for  one  minute. 
The  sample  was  then  allowed  to  remain  perfectly  quiet  and  the  turbidity 
of  the  liquid  determined  at  appropriate  intervals  at  a  point  1/^-inch 
below  its  surface. 


22 


The  electrolytes  used  were  sodium  hydroxide,  acid  carbonate,  car- 
bonate and  chloride;  magnesium  bicarbonate,  and  sulfate;  calcium  hy- 
droxide, chloride  and  bicarbonate;  barium  hydroxide,  Merck's  dialyzed 
iron  and  sulfuric  acid. 

The  effect  of  electrolytes  on  the  stability  of  a  dilute  clay  suspension 
is  similar  to  that  observed  with  clay  slips.  The  results  of  adding  in- 
creasing amounts  of  sodium  hydroxide  is  first  dispersion  followed  by 
coagulation.2  In  Tables  10  and  11  and  Figures  3  and  4  it  is  shown  that 
the  coagulative  powers  of  calcium  and  barium  hydroxide  are  practically 
the  same,  and  that  the  ratio  of  aluminium  to  calcium  and  barium  ions 
is  about  five  to  one.  Data  from  many  of  the  tables  have  been  collected 
and  shown  in  graphic  form  in  Figures  6  and  7.  The  salts  arranged 
according  to  their  efficiencies  as  coagulants  are :  aluminium  sulfate,  cal- 
cium and  barium  hydroxides,  calcium  chloride,  magnesium  sulfate  and 
magnesium  bicarbonate.  Sodium  chloride  has  little  effect  until  its 
concentration  becomes  so  great  as  to  salt  out  the  clay.  Sulfuric  acid 
has  no  apparent  effect  up  to  concentration  of  0.35  milliequivalents  but 
higher  concentrations  coagulate.  (See  Table  16  and  Figure  5.)  Sodium 
hydroxide,  carbonate,  acid  carbonate  and  sulfate  have  at  first  a  stabil- 
izing influence  followed  by  a  coagulating  effect.  The  coagulating  effect 
of  anions  seems  to  be  an  inverse  function  of  their  valencies. 

The  effect  of  added  salts  on  the  coagulation  of  clay  suspensions  by 
aluminium  -sulfate  is  shown  in  Tables  12  to  20,  Figures  8  to  15. 

TABLE  10 — THE  EFFECT  OF  VARYING  STRENGTHS  OF  Naon  ON  THE  RATE 

OF   COAGULATION   OF   CLAY  BY  A12(S04)3. 


Tenn.   No.   3   Ball   Clay — Temperature  ca   23 ( 
Milliequivalents  of  NaOH  added. 


C. 


Milliequivalents 
of  Al. 

0.00 

0.049 

0.09 

0.18 

0.36 

Turbidity. 

Ihr. 

It  hrs. 

Ihr. 

2  hrs. 

Ihr. 

2  hrs. 

Ihr. 

2  hrs. 

Ihr. 

IJhrs^ 

0.0 
.02 
.06 

.09, 

.13 
.17 
.18 
.37 
.55 
.74 
.92 
1.11 
1.29 
1.47 
1.66 
2.03 

420 
420 
400 
150 
125 
125 
100 
100 
125 

420 
400 
400 
75 
75 
50 
50 

420 

400 

420 
420 
400 
350 
175 
275 
375 
450 
300 

400 
360 
360 
375 
50 
150 
175 
350 
250 

450 

400 

450 

400 

450 
420 
300 
200 
200 
400 
420 

420 
420 
240 
75 
40 
400 
375 

420 
150 
100 
100 
100 
100 

400 
100 
90 
85 
85 
80 

400 

400 

350 

350 

50 

75 

400 
300 
75 
300 
250 
190 
125 

60 

275 
200 
75 
125 
90 
90 
50 

150 

60 

100 

75 

240 

100 

420 

125 

150 

75 

90 

50 

200 

50 

350 

100 

150 

50 

23 


TABLE  11 — COMPAKISON  OF  ca(oH)2,  Ba(oH)2,  COLLOIDAL  FE  AND  Al. 

(S04)3   AS    COAGULANTS. 

Tenn.   No.   3   Ball   Clay — Temperature  ca   23°   C. 
Milligram  equivalents. 


A12(SO4)3. 

Turbidity. 

Ca(OH)2. 

Turbidity. 

Ba(OH)2. 

Turbidity. 

Fe. 

Turbidity. 

.02 
.06 
.09 
.13 
.17 
.37 

400 
400 
400 
375 
50 
40 

.26 
.43 
.60 
.69 
.86 
1.03 

400 
390 
350 
350 
150 
100 

.13 
.66 
.79 
1.05 
1.32 

400 
400 
375 
100 
60 

.38* 
3.9 
4.6 
6.1 
6.9 
8.1 

400 

400 
350 
200 
100 
40 

1.38 

50 

9.2 

40 

1.72 

50 

'Parts  per  million. 

TABLE  12 — EFFECT  OF  Na2co3  ON  THE  COAGULATION  OF  A  CLAY 


SUSPENSION  BY  A12(S04)2. 

Tenn.  No.  1  Ball  Clay — Temperature  ca  24' 
Milliequivalents  of  Na2CO3  added. 


C. 


Milliequivalents 
of  Al. 

0.5 

1.0 

Turbidity. 

14  hrs. 

14  hrs. 

14  hrs. 

14  hrs. 

0 
.30 
.45 
.60 
.75 
.90 

400+ 
125 
125 
175 
400 
400 

150 

10 
0 
0 
0 
0 

400+ 
400 
125 
65 
125 
100 

150 
150 
10 
0 
0 
0 

TABLE  13 — EFFECT  OF  Nanco3  ON  THE  COAGULATION  OF  A  CLAY 

SUSPENSION  BY  A12(S04)3. 
Tenn.  No.  1  Ball  Clay — Temperature  ca  24°  C. 


Milliequivalents  of  NaHCOs  added. 


Milliequiva- 
lents of  Al. 

.0 

3 

0.6 

1. 

0 

1. 

* 

li  hrs. 

13  hrs. 

li  hrs. 

13  hrs. 

14  hrs. 

13  hrs. 

14  hrs. 

13  hrs. 

0 
.03 

400+ 
400+ 

325 

275 

400 
400 

400 

375 

400 

300 

400+ 

300 

.06 
.09 

400+ 
400 

150 
150 

400 
400 

300 
275 

400 

200 

400+ 

250 

.12 
15 

350 
275 

75 

75 

300 
225 

100 
65 

350 

200 
5 

400 

150 

.18 
.24 
.30 
.36 

125 
60 
60 

50 
10 
10 

175 
180 
75 
60 

50 
10 
10 
5 

125 
100 
60 
60 

40 
10 
10 
5 

250 

75+ 
75+ 
60 

150 
25 
10 
5 

.42 

60 

0 

60 

5 

75 

5 

.48 

65 

0 

60 

0 

50 

0 

.54 

65 

0 

60 

0 

60 

0 

.60 

60 

0 

60 

0 

.66 

60 

o 

:?§ 

60 

0 

.90 

50 

0 

TABLE  14 — ACCELERATING  EFFECT  OF  Na2so4'oN  THE  COAGULATION  OF 

CLAY  SUSPENSION  BY  A12(S04)3. 

Tenn.  No.  3  Ball  Clay — Temperature  ca  24°  C. 
Milliequivalents    of   Na,SO4   added. 


Milli- 
equivalents 
of  Al. 

1 

2 

3 

4 

Turbidity. 

0 

1* 

24 

1 

24 

« 

24 

1 

24 

.0 
.03 
.06 
.09 
.12 
.15 
.18 

400 
375 
350 
350 
25 

350 
150 
35 
10 
0 

400 

350 

400 

150 

400 
400 
200 
60 
50 

40 
25 
0 
0 
0 

125 
60 
50 

40 

0 
0 
0 
0 

*  Time  expressed  in  hours. 

TABLE  15 — EFFECT  OF  NaCl  ON  THE  COAGULATION  OF  *  CLAY 

SUSPENSIONS  BY  ALUM. 

Tenn.  No.  3  Ball  Clay — Temperature  ca  24°  C. — Tenn.  No.   1  Ball  Clay. 
Milliequivalents   of   NaCl   added. 


Mini- 
equiva- 
lents of  Al. 

1 

3 

10 

1 

2 

Turbidity. 

0 

1* 

24 

1 

24 

1 

24 

li 

12 

Ij 

12 

.0 
.03 
.06 
.09 
.12 

200 
150 
15 
0 
0 

150 
10 
0 
0 
0 

150 
0 
0 
0 
0 

400 
400 
100 
90 
80 

300 
200 
100 
0 
•   0 

400 
400 
400 
80 

250 
200 
60 
0 

400 
350 
100 
25 

350 
175 
50 
40 

50 
50 
50 
50 

*  Time  expressed  in  hours. 

TABLE  16 — THE  EFFECT  OF  VARYING  STRENGTHS  OF  H2so4  ON  THE  RATE 

OF  CLAY  BY  A12(S04)3. 

Tenn.  No.  3  Ball  Clay — Turbidity  420 — Temperature  Ca  23°  C. 
Milliequivalents  of  H0SO4  added. 


Milli- 
equiva- 
lents of  Al. 

0.0 

0.049 

0.09 

0.18 

"  0.36 

Turbidity. 

1  hr. 

2  hrs. 

1  hr. 

2  hrs. 

1  hr. 

1|  hr. 

1  hr. 

IJ  hr. 

1  hr. 

li  hr. 

0.000 
.02 
.06 
.09 
.13 
.17 
.18 
.37 
.55 
.74 
.92 

420 
420 
400 
150 
125 
125 
100 

420 
400 
400 
75 
'  75 
75 
50 

420 

420 

420 
400 
370 
200 
150 

400 
375 
310 
60 
60 

420 
400 
290 
240 
140 

400 
400 
1  150 
100 
60 

420 

250 

375 

200 

360 
150 
100 

350 
90 
60 

150 

50 

150 
100 

50 
60 

140 
125 
100 

50 
50 
50 

75 
75 
50 

•  50 
50 
50 

150 
200 
200  ( 

50 
50 
50 

125 

50 

150 

60 

TABLE  17— -EFFECT  OF  Mgso4  AND  Mg(HC03)2  ON  THE  COAGULATION  OF 

CLAY  SUSPENSIONS  BY  A12(S04)3. 

Tenn.  No.  1  Ball  Clay — Temperature  ca  24°  C. 
Milliequjvalents  of  MgSO4  added. 


Milliequiva- 
lents  of  A). 

1 

2 

3 

Turbidity. 

11  hrs. 

14  hrs. 

11  hrs. 

14  hrs. 

11  hrs. 

14  hrs. 

0 
.009 
.018 
.030 
.036 
.060 
.090 
.120 

400 

100 

350 

50 

325 
400 
175 
150 
125 
100 

15 
15 
10 
0 
0 
0 

200 

25 

150 

10 

125 
125 
125 
100 

10 
0 
0 
0 

150 
125 
125 

0 
0 
0 

TABUE  18 — MILLIEQUIVALENTS  OF  Mg(HC03)2  ADDED. 


Milliequiva- 
lents  of  Al. 

1 

2 

3 

Turbidity. 

11  hrs. 

14  hrs. 

11  hrs. 

14  hrs. 

11  hrs. 

14  hrs. 

0 
.009 
.018 
.030 
.045 
.060 
.090 
.120 

400 

150 

400 

85 

350 

350 
300 
275 
250 
125 

65 
30 
25 
20 
15 
15 

80 
35 

350 

125 

350 

250 
175 
125 

25 
15 
10 

10 
0 

• 

150 

1 

TABLE  19  —  EFFECT  OF  CaCl2  THE  COAGULATION  OF  CLAY  SUSPENSIONS 

BY  A12(S04)3. 

Tenn.  No.  1  Ball  Clay  —  Temperature  ca  24°  C. 
Milliequivalents  of  CaCl,. 

Milliequiva- 
lents  of  Al. 

1 

2 

3* 

Turbidity. 

11  hrs. 

14  hrs. 

11  hrs.    - 

14  hrs. 

11  hrs. 

14  hrs. 

0 
.009 
.010 
.030 
.045 
.060 
.090 
.120 

400 

125 

185 

10 

175 
175 
175 
200 
175 
125 

10 
10 
5 
0 
0 
0 

185 
180 

5 
0 

300 

25 

175 
125 
175  (?) 

10 
5 

0 

175 
175 
175 

0 
0 
0 

TABLE  20 — EFFECT  OF  ca(Hcos)2  ON  THE  COAGULATION  OF  CLAY 

SUSPENSIONS  BY  A12(S04)3. 

Tenn.   No.   1   Ball  Clay — Temperature   ca   23°    C. 
Milliequivalents  of  Ca(HCO3),. 


Milliequiva- 
lent  of  Al. 

0 

1 

0 

2 

Time  in  hours  and  turbidity. 

H 

13 

li 

13 

ii 

13 

u 

13 

0 
.009 
.018 
.030 
.045 
.060 
.090 
.120 

325 

325 

125 

200 
200 
150 
150 
125 

200 

75 
50 
40 
25 

25 
10 
5 
0 
0 

175 

10 
0 
0 

325 

125 

200 

15 

325 
75 
50 

70 
10 
0 

75 
50 
50 

10 
5 
0 

i 

.06  -/«  *I8  -55  -9Z 

Scale  I  div.  -  .006_1*_  Scale  I  div.  -  .037 


:+ 


/.  29  /.  67         2.03 


Milliequivalents  of  Aluminium. 
Figure  3.  —  Effect  of  NaOH  on  the  coagulation  of  a  clay  suspension  by  A1.,(SO4), 


Time  of  seff//nj  =  one  hour. 


Milliequivalents  .of  Aluminium. 

Figure   4. — Comparison  of  A12(SO4)3,   colloidal  Fe,   Ca(OH)2,   lia(OH),  as 

coagulants. 


27 


32&A 

3/V) 

Tlme  of  sett/tnq  > 

ijfoZ  hours 

Legend 
no  millieyuiva/enfs  of  Hf5Q^  added. 
.09  mjlliequ/m/cnts  ofH^^O^added- 
.  36rni//ieqw  vafarfc  tf/jJQf  added. 

5 

A- 

o- 
x- 

ZOO— 

I 

100- 

\ 

k 

f  * 

* 

^ 

-o- 

e  — 

Mmjeouiva/enfe  of  Aluminum 

Figure  5. — Effect  of  H2SO4  on  the  coagulation  of  clay  suspension  by  Al2(SO4)r 


o  .2  .4 

Scate  I  dry.'  .020 


1.0  2.0  3.0  4.0 

Scale  1  div.  *  .100 


Milliequivalents  of  Electrolytes. 
Figure  6. — Effect  of  electrolytes  on  the  coagulation  and  settling  of  clay  suspensions. 


•a 


3 

Dd 

<w 

o 

*s 

9 


HaOH 

ra 

p  A 

500    /, 

S^— 

\ 

£ 

200 

MaCl 

NozSOj. 

V 

A 

^^ 

/Vo  50//5 

^ 

foo     Jjfc 

^v  v 

A'oC/ 

g(HCO3)2 

\ 

^^ 

^N 

S 

^  , 
kM75^ 

•\ 

'     3-^//<?£ 

y  y^/7/3-. 

<?  /.  r.  j.  4:          5»  «. 

Milliequivalents  of  Electrolytes. 
Figure  7. — Effect  of  electrolytes  on  the  coagulation  and  settling  of  clay  suspensions. 


28 


Figure  7 


.03  .06  .09  .12  .36  .60  .84 

Scale  I  div.  •  .003          »[<        Scale  I  Ctiv.  =•  .O24 

Milliequivalents  of  Aluminium. 

"A".  —  The  effect  of  the  addition  of  one  milliequivalent  of  electrolytes  on 
the  coagulation  of  clay  suspension  by  A1,(SO4)3. 


o  Time  settling  I  hour 
•  T/me  settling  *  £4 hours. 


LO'tlilliequlva/enf  of  N^ 


f 

3(7(7 


Milliequivalen, 


.03  .06 

Milliequivalents  of  Aluminium. 
Figure  8. — Effect  of  Na2CO3  on  the  coagulation  of  clay  suspensions  by  A12(SO4)S. 


I        I        ,        Hme  of  sett  liny  /i  hours 

, 

Itoo9 

3OO 

c 

^XJ 

V 

N 

4 

bAk 
KO* 
°J.5 

X, 

'  mill/equ/vaknts  ofNaHCOg 
^      n            a         n       " 

II                                    /I                        H                   It 

?on 

\ 

s 

N^ 

^s 

/CO 

N 

\ 

\ 

^ 

•  —  .. 

1  —  o- 

^s 

k 

•"^IM  M 

^ 

* 

3    (7      .03     .06     .Of     ./£ 


^75   .<V     ./Z     ./^     /<?    .£/     .£4    .27     30    .33    .36 

Milliequivalents  of  Aluminium. 
Figure  5. — Effect  of  NaHCO3  on  the  coagulation  of  clay  suspension  by  Al.j(SO4)3. 


30 


o  77me  of  seft/ing=  one  hr    ' 
+  Time  of  settling  =£4  hrs. 


3OO 

V 

nillit 

:auivz 

-.of/ 

U&5 

(% 

•PfJfi 

\ 

-100 

*"  —  \ 

\ 

'•«  ..  ^J 

\ 

^  —  c 

> 

.03      '06      .09 


Turbidity  of  Suspension 

*toa< 

300 

'mil/i 

i  • 

'ec/uiv.  of 

'NaGI. 

s 

\ 

\ 

V/7/7— 

^\ 

\ 

s 

k»^  > 

N 

> 

O     .03    .06     .09    .12.  1     ,03    .06     .09    7Z 

Milliequivalents  of  Aluminium. 

Figure  10. — Effect  of  Na,SO4  and  NaCl  on  the  coagulation  of  clay  suspension  by 

A12(S04),. 


31 


ZT/^:/  of  CdC/? 


Milliequivalents  of  Aluminium. 

Figure  11. — Effect  of  Mg(HCO3)2  and  of  CaCl,  on  the  coagulation  of  clay 
suspension  by  A1,(SO4)3. 


ilJ 


O   o 


p 

II 


33 


III! 


O    g 
C    O 


34 


ox 

w  <& 
^•"3 

•<  o 


35 


400- 


Time  of  sett// nq  /j? hours 
Co^fro/. 


A-  No 


o  -  CaflCOj)t  present 


.03  .06  .07  ./2 

Milliequivalents  of  Aluminium. 

Figure   15. — Effect  of  Ca(HCO3)0  on   the  coagulation   of  clay  suspensions 

by  A13(S04)8. 

As  would  be  expected  the  presence  of  the  trivalent  and  bivalent 
ions  aid  in  the  coagulation,  sodium  chloride  and  sulfuric  acid  have  little 
effect  at  low  concentrations,  while  the  addition  of  the  sodium  salts 
causes  a  behavior  similar  to  that  produced  by  the  action  of  sodium  hy- 
droxide (Figure  3). 

As  the  content  of  sodium  hydroxide  is  increased  the  amount  of 
aluminium  sulfate  must  be  increased  in  order  to  produce  coagulation  and 
to  combat  the  dispersive  power  of  the  sodium  compound.  This  same 
effect  is  quite  noticeable  with  sodium  carbonate  but  less  so  with  sodium 
acid  carbonate  and  sulfate. 

The  point  of  coagulation  is  not  dependent  on  the  alkalinity  of  the 
solution.  The  results  of  these  experiments  are  partly  in  accordance  with 
work  and  theories  of  Rohland.40'42  There  seems  to  be  no  question  but 
that  coagulation  is  a  function  of  the  concentration  of  the  hydroxyl  ion 
and  alkali  metal  ions  as  well  as  the  valencies  of  the  cation. 

The  monovalent  ion  of  the  alkalies  is  intimately  connected  with  the 
dispersive  or  protective  action  of  sodium  salts  in  the  coagulation  of  clay 
suspensoids  and  with  the  peculiar  (Protective)  effect  of  silicic  acid  in 
preventing  the  formation  of  aluminium  hydroxide  by  the  action  of 
aluminium  chloride  and  sodium  hydroxide.  If  .calcium  is  substituted 
for  sodium  these  peculiar  effects  are  not  produced. 

The  effect  of  silicic  acid  on  the  coagulation  of  clay  suspensions  by 
aluminium  sulfate  is  shown  in  Tables  21,  22,  and  23,  and  Figures  15 
to  19.  A  suspension  containing  62  parts  per  million  of  dialyzed  silicic 
acid  and  appropriate  amounts  of  electrolytes  were  coagulated  with  alum 
and  the  rate  of  reaction  compared  with  a  suspension  containing  no 
added  silicic  acid.  In  all  cases  the  effect  of  the  added  silicic  acid  was 
to  retard  the  reaction,  and  more  aluminium  sulfate  was  required  to  pro- 


36 

duce  coagulation  than  before — regardless  of  the  presence  or  absence  of 
electrolytes.  Photographs  (Figures  20  and  21)  were  taken  five  "days 
after  the  addition  of  the  aluminium  sulfate.  Silicic  acid  was  added  to 
the  samples  on  the  right.  The  data  given  in  Tables  19  and  20  was  ob- 
tained from  this  experiment. 

The  aluminium  consumed  is  a  function  of  the  silicic  acid  added, 
but  the  mathematical  relationship  is  not  a  simple  one  and  varies  with 
the  clay  used.  This  relationship  is  shown  in  Figures  15  and  17,  which 
have  been  plotted  from  data  in  Tables  21  and  22.  In  general  the  amount 
of  aluminium  required  to  coagulate,  per  unit  amount  of  silicic  acid 
added,  is  larger  at  low  than  at  high  concentrations.  Silicic  acid  does 
not  seem  to  stabilize  or  disperse  the  clay  particles,  nor  does  its  presence 
influence  the  rate  of  sedimentation.  In  this  respect  it  differs  from  the 
alkali  salts. 

TABLE  21 — RETARDING  EFFECT  OF  SILICIC  ACID  ON  THE  COAGULATION 

OF    CLAY  SUSPENSION   BY   A12(S04)3. 

Tenn.  No.  3  Ball  Clay— Temperature  ca  24°C. 
Silicic  Acid  (SiO2)  added. 


Milligram 
equiva- 
lents. 

0  ppm.* 

12.4  ppm. 

24.8  ppm. 

37.2  ppm. 

49.6  ppm. 

Turbidity. 

I*** 

13 

11 

13 

11 

13 

tl 

13 

li 

13 

.0 
03 
06 
09 
12 
15 

400 
400 
400 
125 
75 

225 
150 
125 
10 
5 

400 

225 

400 

250 

400 

275 

400 

275 

400 
400 
50 
50 

175 
150 
10 
10 

400 

250 

400 

275 

400 

275 

125 
50 
50 

75 
20 
10 

175 

125 

225 

125 

50 
60 
50 

20 
10 
10 

50 
50 
40 
25 

25 
10 
10 
10 

The  Amount  of  Alum  Necessary  to  Produce  a  Definite  Clarification  in  13  Hours  in  the  Presence  of 

Silicic  Acid. 


*  Parts  per  million. 
**  Time  expressed  in  hours, 
t  Milligram  equivalents. 


Ah  (864)3  added  to  reduce  turbidity  to 


SiO2  added. 

100  ppm. 

50  ppm. 

10      ppm. 

.07f 

.084* 

12.4  ppm. 

.102 

.111 

24.8  ppm. 

.112 

.129 

37.2  ppm. 

.126 

.153 

49.7  ppm. 

.129 

15.3 

37 


TABLE  22 — EETARDING  EFFECT  or  SILICIC  ACID  ON  THE  COAGULATION 

OF   CLAY  SUSPENSION  BY  A12(S04)3. 

Tenn.  No.  3  Ball  Clay— Temperature  ca  24°C. 
Silicic  Acid  (SiO2)  added. 


Milligram 
equiva- 
lents. 

0  ppm.* 

12.4  ppm. 

24.8  ppm. 

37.2  ppm. 

49.6  ppm. 

Turbidity. 

1** 

24 

1 

24 

1 

24 

1 

24 

• 

24 

.03 
.06 
.09 
.12 
.15 
.18 
.21 
.24 
.27 
.30 
.33 
.39 
.45 
.51 

400 
400 
175 
30 

200 
150 
5 
5 

350 
325 
200 
75 
40 
40 

166 

50 
25 
5 
5 
5 

350 
350 
350 
350 
212 
100 
50 
40 
40 

350 
350 
350 
125 
50 
50 
50 

50 
50 
50 
25 
10 
5 
5 

100 
100 
100 
40 
30 
20 
5 
5 

200 

75 

100 

50 

50 
25 
20 
20 

20 
15 
12 
10 

The  Amount  of  Ah  (864)3  Necessary  to  Produce  a  Definite  Clarification  in  One  Hour  in  the  Presence 

of  Silicic  Acid. 


*  Parts  per  million. 
**  Time  expressed  in  hours. 
4-  Milligram  equivalents. 


A12(SO4)3  added  to  reduce  turbidity  to 


SiO2  added. 

100  ppm. 

50  ppm. 

0 

.105+ 

.115+ 

12.4  ppm. 

.174 

.200. 

24.8  ppm. 

.210 

.240 

37.2  ppm. 
49.6  ppm. 

.240 
.270 

.270 
.330 

38 


TABLE  23 — EETAEDING  EFFECT  OF  SILICIC  ACID  ON  THE  COAGULATION 
OF  CLAY  SUSPENSIONS  BY  A12(S02)3  IN  THE  PRESENCE  OF  ELECTRO- 
LYTES. 
Term.  No.  1  Ball  Clay— Turbidity  400  parts  per  million— Temperature  ca  21°  C— Time  3  hours. 


Milli- 
equivalent 
of  Al. 

Milligram  equivalents  of  salts. 

.  18  NaOH. 

1.5  NaHCOs. 

2  NaCl. 

2  Na2SO4 

2  Mg(HC03)2. 

Dialyzed  silicic  acid,  parts  per  million  as  SiO2. 

0 

62 

0 

62 

0 

62 

0 

62 

0 

62 

.03 
.06 
.09 
.12 
.15 
.18 
.21 
.27 
.30 
.36 
.39 
.45 
.60 

350 
350 
325 
225 

400 
400 

400 

400 
400 
350 
25 

400 

350 

75 

350 

400 

25 

400 
25* 
25 

400 

400 

35 

125 

300 

350 
25 

10 

10 

85 

400 

35 

15 

125 

10 

65 

350 

0 

65 

300 

' 

Milli- 
equivalent 
of  Al. 

Milligram  equivalents  of  saits. 

2  MgSO4. 

0.7  Ca(OH2).* 

1.0  Ca(HC03)2. 

0.7  CaOH2f 
1.0  ca 
(HCOa)2. 

Dialyzed  silicic  acid,  parts  per  million  as  SiO2. 

0 

62 

0 

62 

0 

62 

0 

62 

.03 
.06 
.09 
.12 
.15 
.18 
.21 
.27 
.30 
.36 
.39 
.45 
.60 

400 
400 

85 
85 
85 
125 
100 

180 
180 
170 
170 
160 

350 
100 
65 
65 

400 

400 
400 
400 

175 

400 

50 

250 

350 

50 

150 

175 

325 

25 

65 

150 

250 

*  13  hours. 

t  Readings  expressed  as  turbidities. 


39 


O     03    .06    W     ,IZ    .15    /&.  0     .03    .08     JW    .12.     ./ff     /S    .&     .24     </ 

Milliequivalents  of  Aluminium. 

The  amount  of  Aluminium  necessary  in   the   presence   of  silicic   acid    to   produce   a 

definite  clarification. 

Figure  16. — Effect  of  silicic  acid  on  the  coagulation  of  clay  suspension  by  Al,(Sn,)t. 


<4OO* 

y.  r/mef   of  sett  f  ing  *  /hour 
o  Time  of  settling  "24  hours 

\ 

J 

' 

\ 

No 

•\ 

*J/(/Z> 

_4 

pn* 

5en1 

zoo 

//yi 

SiO,  -j. 

*4fi 

LLILL 

rj. 

5 

N  x\ 

fvr' 

MN 

( 

| 

"—  ] 

IJx, 

f        N 

\         i         t 

.09     M      ,15     .16      .21      .24     .Zl     .30 


0      .01     -IZ    .&     JO     £1     .01-     .Of     JZ     .15     .16     .21     ^4    .£?    .30 

Milliequivalents  of  Aluminium. 
Figure  17. — Effect  of  silicic  acid  on  the  coagulation  of  clay  by  A12(SO4), 


40 


.03     .06    .09      OJZ    .15     J8      £1      £4     .27    .30    .33 

Milliequivalents  of  Aluminium. 

Figure  18.— Al  necessary  to  produce  a  definite  clarification  in  the  presence  of  silicic 
acid.     Plotted  from  Figure  14. 


Legend 
r  Zwtilliequhatefrh  of 


300 


.2  0       J05      .00      .09      ./S       /5      JO       £1       -34-       .27       30    .35 


Mill/equivalents  of  Aluminum 


Legend. 

X      0.18 mi  Hi  equivalents  NaOfi 
O     O.ldmillieyuivalenf5  NaOH  +6£f>.pm.  5iOx 


400 
3OO 
SOO 
ICO 

t 

~\  T 

l.5millie^ 

«,v. 

'Gf//J  /K7//1 

yaHC03-h 

&n 

\m 

PL! 

^ 

r~-\ 

I 

\; 

\ 

T 

\ 

x 

> 

\ 

\ 

\ 

^ 

7       .C 

v    .0 

6     .6 

9     ./ 

f      .19     .18      .fl      .24      .&      30     .33    .J6      .39 

Mi  1 1 /equivalents   of  Aluminum 


Figure  19. — Effect  of  sodium  salts  on  the  coagulation  of  clay  suspension  by 
A1,(SO4)3  in  the  presents  of  silicic  acid. 


300+ 
300 
200 
.    ,00 

ft 
ft 

.s 

§ 

N 

\ 

—i^ 

^ 

«2J. 

\ 

\ 

vs 

Vr 

s 

> 

1 

^ 

>  

—  —  ^ 

71 

H     — 

—  —  , 

I 

?      .03     .06      .09       .f2     .Iff      J6        0      .03       .06     .09       72      ,/S    -16 

2  Flillieauivs.  WgCHCOj)                 £  Milliequivs.  Hg504 

400 
3OO 

zoo 

100 

5/C 

f  6< 

Vv0' 

77. 

( 

V 

\ 

1 

s-^ 

fc  4 

i 

.09     ./£      ./5" 


JO     .09      .06     .03     Jt      J5      JO      .21 


I  Mil/icqu/v.  Ca(0ff)z 


.  Ca(HCO,) 


.O.J 
1.0 

Milliequivalents  of  Aluminium. 

Figure    20.  —  Effect   of   silicic   acid   on   the   coagulation   of   clay    suspensions   in   the 

presence  of  Electrolytes. 


m 

5 

eo 


II 

i  § 

735 

73 

o  c 

la 

s    s 

01  o 

j§      -3 


Electrolytes 
Mgr(HCOs)2 


NaHCOs 


Absent.  Present. 

Colloidal  Silicic  Acid. 

Figure  22. — The  effect  of  silicic  acid  on  the  coagulation  of  clay  suspensions 

by  A12(SO4)3. 

APPLICATION. 
Removal  of  Silicic  Acid   From  Water  to  be  Used  for  Boiler  Purpose, 

The  experiment  on  a  natural  water  already  referred  to  indicates 
that  silicic  acid  could  be  most  economically  removed  by  aluminium  hy- 
droxide formed  in  the  reaction  of  aluminium  sulfate  with  calcium  hy- 
droxide in  a  solution  whose  Ph  value  is  8.0  —  9.0,  and  that  the  precipi- 
tation is  more  or  less  directly  related  to  the  ratio  of  (Ca  +  Mg)  :  Na. 
The  higher  this  ratio  the  more  complete  is  the  removal.  By  the  proper 
treatment  with  aluminium  sulfate  and  line  it  is  possible  to  reduce  the 
silicic  acid  content  from  82.6  to  30  parts  per  million. 

The   Coagulation    of  Waters   Containing    Colloidal   Clay. 

The  stability  of  a  suspension  of  clay  seems  to  be  intimately  con- 
nected with  the  amount  of  monovalent  cations  and  bivalent  anions  pres- 
ent. Thus  the  alum  needed  to  coagulate  will  be  greater  the  larger  the 
concentration  of  sodium  ions  except  in  the  case  when  the  anion  is  mainly 
chlorine.  Less  alum  will  be  needed  as  the  ratio  of  the  Ca  +  Mg  ions 
to  the  sodium  ion  increases.  As  the  silicic  acid  content  increases  more 


44 

alum  will  be  required  to  coagulate.  In  concentrations  up  to  20  parts 
per  million,  from  0.015  to  0.03  milligram  equivalents  of  aluminium 
(Al)  per  10  parts  of  Si02  is  needed  to  combat  the  influence  of  the  silicic 
acid. 

Rate  of  Reaction. — Water  containing  bivalent  ions  when  treated 
with  alum  gives  a  sharp,  abrupt  reaction,  an  increase  of  0.3  milligram 
equivalents  of  aluminium,  Al,  coagulates,  but  when  silicic  acid  or  alka- 
lies are  present,  other. factors  being  constant,  a  much  larger  amount  of 
alum  is  necessary  to  produce  the  same  clarification  and  the  abruptness 
of  the  reaction  becomes  less  as  the  amount  of  the  silicic  acid  and  alkalies 
approaches  a  certain  maximum  where  the  magnitude  of  the  change  pro- 
duced per  unit  amount  of  alum  is  much  smaller  than  in  the  former 
case. 

This  is  well  shown  in  Figures  8,  9,  12,  14,  15,  and  21.  This  phe- 
nomenon is  exactly  similar  to  that  which  occurs  when  "colloidal  waters" 
are  coagulated  by  alum  and  lime. 

These  experiments  justify  the  addition  of  an  excess  of  calcium  hy- 
droxide, Ca(OH)2  and  allowing  it  to  react  with  the  water  for  some  time 
(8  to  12  hours)  before  the  addition  of  the  alum  or  ferrous  sulfate. 
This  procedure  has  been  effective  in  purification  of  water  from  the 
Arkansas  River  at  Little  Rock,  Arkansas  when  the  suspended  material 
is  in  a  colloidal  state. 

SUMMARY. 

1.  Colloidal  silicic  acid  in  dilute  solution  can  be  precipitated  by 
aluminium  hydroxide. 

2.  Dilute  solutions  of  dialyzed  and  undialyzed  silicic  acid  behave 
towards  electrolytes  in  the  same  manner  as  concentrated  solutions — 
with  the  exception  that  proportionately  more  reagent  is  needed. 

3.  The  optimum  hydrogen  ion  concentration  for  the  precipitation 
of  the  aluminium  hydroxide  and  the  removal  of  silicic  acid  by  aluminium 
hydroxide  is  a  concentration  of  1  x  10~8. 

4.  The  limiting  values  of  the  hydrogen  ion  concentration,  between 
which  the  solid  aluminium  hydroxide  phase  is  present  are  1  x  lO^4  and 
11  x  10-11. 

5.  The  presence  of  silicic  acid  prevents  the  formation  of  a  preci- 
pitate of  aluminium  hydroxide,  when  the  sodium  hydroxide,  equivalent 
to  the  aluminium  chloride  present,  is  added  all  at  once.    The  silicic  acid 
probably  as  a  protective  colloid  prevents  precipitation  of  the  alumi- 
nium hydroxide.     The  presence  of  bivalent  cations  destroys  this  pro- 
tective power. 

6.  The  action  of  electrolytes  on  clay  suspensoids  is  the  same  in 
dilute  as  in  concentrated  suspensions.     (Slips). 


45 

7.  Sodium  hydroxide,  acid  carbonate,  and  sulfate  stabilize  or  dis- 
perse clay  suspensions  at  one  concentration  and  coagulate  at  another. 

8.  The  ratio  of  the  coagulating  power  of  calcium  and  barium  hy- 
droxide to  aluminium  hydroxide  is  about  1  to  5. 

9.  Coagulation  of  clay  suspensions  is  aided  by  the  bivalent  and 
hindered  by  monovalent  cations  in  the  presence  of  acid  carbonate,  car- 
bonate, sulfate  and  hydroxyl  anions. 

10.  Silicic  acid  retards  coagulation  of  clay  suspensoids. 

REFERENCES. 

1.  Ashley,   H.   E.,   The   colloid  matter  of  clay   and   its  measurements,   U.   S. 

Geol.  Surv.  Bull.  388   (1909). 

2.  Ashley,  H.  E.,  The  technical  control  of  the  colloid  matter  in  clays,  Trans. 

Am.  Ceram.  Soc.  12,  768    (1910). 

3.  Audley,  J.  A.,  Some  casting  slip  troubles,  Trans.  Eng.  Ceram.  Soc.  14,  152 

(1914-15). 

4.  Billitzer,  Jean,  Theorie  der  Kolloide,  Z.  Physik.  Chem.  51,  150   (1905). 

5.  Billitzer,    Jean,    Theorie    der    Kolloide,    Ber.    Wien    Akad.   Wiss.    113.  (II) 

1159    (1904). 

6.  Back,    Robert,    Effect    of   some    electrolytes    on    clay,    Trans.    Am.    Ceram. 

Soc.  16,  515   (1914). 

7.  Black   and   Veatch,   Whipping  chemicals  into   a   colloidal   water   increases 

efficiency,  Eng.   Record,  72,   292    (1915). 

8.  Bleininger,  A.  V.,  The  effect  of  electrolytes  upon  clay  in  the  plastic  state, 

Orig.  Com.   8th.  Intern.  Cong.  Appl.  Chem.  5,  17. 

9.  Blitz,  Wilhelm,  Ueber  die  gegenseitige  Beeinflussung  colloidal  Stoffe.     Ber. 

cl.  d.  chem.  Gesell.  37,  1095    (1904). 

10.  Burton,   E.   F.,   The  action   of  electrolytes   on  colloidal   solutions,  Phil.   M. 

228,   12,   472    (1906). 

11.  Burton,   E.   F.,   The   physical   properties   of   colloidal   solutions,   p.    1,   New 

York,  1916. 

12.  Catlett,  George  F.,  Colloidal  theories,  applied  to  colored  water,  reduce  cost 

of  chemicals.     Eng.  Record,  73,  741   (1916). 

13.  Crook,  J.  K.,  Mineral  waters  of  the  United  States,  p.  347,  New  York,  1899. 

14.  Clark  and  Lubs,   The  colorimetric  determination  of  hydrogen  ion   concen- 

tration and  its  application  in  bacteriology,  J.  Bact.  2,  Nos.  1,  2,  3. 

15.  Crum,    W.,    Ueber    Essigsaure    und    andere    Verbindungen    der    Thonerde, 

Ann.  d.  chem,  u.  pharm.  89,  156   (1854). 

16.  Dole,  R.  B.,  The  quality  of  surface  waters  in  the  United  States,  U.  S.  Geol. 

Surv.,  Water  Supply  Paper,  236   (1909-10). 

17.  Ellms.     The  coagulation  and  precipitation  of  impurities  in  water  purifica- 

tion, Eng.  Rec.  51,  552   (1905). 

18.  Foerster,  F.,  Ueber  das  Giessen  des  Tons,  Chem.  Ind.  28,  733    (1905). 

19.  Fleming,  W.,  Gerinnungsgeschwindigkeit  kolloidaler  Kieselsaure,  Z.  physlk. 

chem.  41,  443   (1902). 

20.  Fuller.  Water  purification   at  Louisville,  Ky.,  and  Cincinnati,   Ohio. 

21.  Goldberg,   A.,   Die   Kieselsaure   im    naturlichen   Wasser,    in   Alkalisch   aus- 

gereinigten   Kesselspeise   Wassern   und   in   konzentrierten    Kesselwasser, 
Z.  Nahr.  Genussm.  27,  265   (1914). 

22.  Hardy,  W.  B.,  On  the  mechanism  of  gelatin  in  reversible  colloidal  systems, 

Proc.  Royal  Society   (London),  66,  95    (1900). 

23.  Hardy,  W.  B.,  Colloidal  solution,  the  globulins,  J.  Physiol.  33,  258    (1905). 

24.  Hardy,  W.   B.,   Structure   of  cell  protoplasm,   J.    Physiol.   24,    180    (1899). 

25.  Hardy,  W.  B.,  Eine  vorlilufige  Untersuchung  der  Bedingungen,  welche  die 

Stabilitat    von    nicht    umkehrbaren    Hydrosolen    bestimmen,    Z.    physlk. 
Chem.  33,  391    (1900). 

26.  Hillebrand,   W.   F.,    The   analysis   of   silicate   and   carbonate   rocks,   U.    S. 

Geol.  Surv.  Bull.  422,  13. 


46 

27.  Japp,  F.  R.,  and  Murray,  T.  S.,  Synthesis  of  pentaCarbon  rings,  J.  Chem. 

Soc.  71,   148    (1897). 

28.  Lottermoser,   A.,    Beitrage    zur   Kenntnis   des    Hydrosol-und    Hydrogelbild- 

ungsvorganges,  Z.  physik.  Chem.  60,  451    (1907). 

Ueberflihrung  einiger   Metalle    in    den    Kolloi'dalen   Zustand   und   Eigen- 
schaften  derselben.     Phys.  Zeitung,  /,   148    (1899). 

29.  Linder   and   Picton,    Solution,  and    pseudo    solution    (sulphides),    J.    Chem. 

Soc.   (London),  61,  148;  67,  63;  71,  568;  87  (pt.  4),   (1906). 

30.  Mayer,    A.,    Schaffer,    G.,    and    Terroine,    E.,    Influence    de    la    reaction    du 

milieu  sur  la  grandeur  des  granules  colloi'daux,  Compt.  Rend.  145,  918 
(1907). 

31.  Mellor,  Green  and  Baugh,  Studies  on  Clay  slips,  Trans.  Eng.  Ceram.  Soc. 

6,  161    (1906).  , 

32.  Kahlenberg,  L.,  and  Lincoln,  A.  T.,  Solutions  of  silicates  of  the  alkalines, 

J.  Phys.  Chem.  2,  77   (1898).       \ 

33.  Kerr  and  Fulton,  The  effects  of  some  electrolytes  on  typical  clays,  Trans, 

Am.  Ceram.  Soc.  15,  184   (1913). 

34.  Kuspert,   F.,   Ein  Demonstrationsversuch  ueber  colloi'dales   Silber,   Ber.   d. 

d.   chem.   Gesell,   35,   2815    (1902). 

35.  Pappada,  N.,  Sulla  Coagulazione  Dell'  acido  silicies  colloidale,  Gazz.  chim. 

Hal.,  33,  II,  272    (1903),  35,  I,  78   (1905). 

36.  Parmelee   and   Moore,    Some   notes   on    the   mechanical   analysis   of    Clays, 

Trans,  Am.  Ceram.  Soc.  II,   467    (1909). 

37.  Peale,   S.   C.,  Lists  and  analyses  of  United  States  mineral  waters,   U.   S. 

Geol.  Surv.  Bull.  32,  35    (1886). 

38.  Pence,  F.  K.,  Trans.  Am.  Ceram.  Soc.  12,  43    (1913). 

39.  Quincke,    G.,    Ueber    die    Fortfiihrung   materieller    Theilchen    durch    strft- 

mende  Elektricitat,  Ann.  physik.  u.  Chem.  II,  115,  513  (1861)  ;  Tereschin,' 
S.  Ann.  Physik.  Ill,  32,   333    (1887). 

40.  Rohland,   Paul,   Ueber   die   Einwirkung  von   Hydroxlionen   auf   Kaolinsus- 

pensionen,  Z.  Chem.  ind.  Colloide  II,  193. 

41.  Rohland,   Paul,   Eine  Kolorimetrische  Methode  zur  Bestimmung  der  Kol- 

loidstoffe  in  Abwassern,  Z.  Anal.   Chem.  52,   657. 

42.  Rohland,  Paul,  Das  Verhalten  der  Tone  und  Kaoline  gegen  Hydroxylione, 

Biochem,  Z.  58,  202,   (1913-14). 

43.  Schultz,   H.,   Schwefelarsen  in   wassriger  Losung,   J.   F.   prakt.  Chem.    (2) 

25,  431  (1882)  ;  Antimontrisulfid  wasserigen  Losung  27,  320  (1883)  ; 
ueber  das  Verhalten  von  seleniger  zu  schwefliger  Saure.  32,  390  (1884). 

44.  Schwerin,    Ein    neues    elektrishes    Tonreinigungsverfahren     (von    Dr.    M. 

Stoermer),  Tonind.   Zeitung,  36,  1283. 

45.  Thomas,   Settling  and  filtering  of  fine  clays,   Trans.  Am.   Ceram.   Soc.   14, 

399    (1912). 

46.  Tirelli,  L.,  Effect  of  free  silica  in  water  used  industrially,  Rass.  min.  26, 

134-36. 

47.  Tyndall,  John,  On  the  blue  colour  of  the  sky,  and  on  the  polarization  of 

light,  Phil.  M.    (4),  37,  384    (1869). 

48.  Van   Bemmelen,   J.   J.,   Die  Verbindungen   einiger   fester   Dioxhydrate   mit 

Sauren,  Salzen,  und  Alkalien,  J.  prakt.  Chem.  2d.  Ser.,  23,  324,  379 
(1881). 

49.  Weber,  E.,  The  liquefaction  of  clay  by  alkalies,  and  the  use  of  fluid  clay 

casting  in  the  ceramic  industry,   Trans.  Eng.   Ceram.   Soc.  8,   11. 

50.  Whitney  and   Ober,   The   precipitation   of  colloids  by  electrolytes,   J.   Am. 

Chem.  Soc.  23,  842   (1901). 

51.  Wiederrian,    G.,    Ueber    die    Bewegung    von    Fliissigkeiten    im    Kreise    der 

geschlossenen  galvanischen  Saule,  Ann.  d.  Physik,  u.  Chem.  II,  187, 
321  (1852). 

52.  Zimmer,  W.  H.,  Hydrated  silicic  acid  in  kaolin  and  its  effects  in  pottery 

bodies,  Trans.  Am.  Ceram.  Soc.  3,  25   (1901). 

53.  Zsigmondy  and  Siedentopf,  Vortrage  und  Diskussionen  von  der  77  Natur- 

forscherversammlungen  zu  Meran,  Phys.  Z.  6,  855  (1905)  ;  ueber  aml- 
krospische  Goldkeime,  Z.  Wiss.  Mikros,  24  (1907)  ;  Physik.  Z.  8,  850 
(1907). 


VITA. 

The  author  was  born  in  Yates  Center,  Kansas,  May  12,  1884,  and 
received  his  early  education  in  the  public  schools  of  Green  County, 
Missouri,  graduating  from  the  Springfield  High  School  in  1903.  In 
the  fall  of  that  year  he  entered  Drury  College,  Springfield,  Missouri, 
and  in  1907  received  the  degree  of  Bachelor  of  Science.  For  the  term 
of  1907-08  he  taught  Chemistry  and  Physics  in  the  Springfield  High 
School.  The  following  two  years,  1908-1910,  were  spent  as  a  graduate 
student  in  chemistry  at  the  University  of  Pennsylvania.  In  Septem- 
ber, 1910,  he  entered  the  employment  of  the  Iowa  State  College  as 
assistant  chemist  for  the  Engineering  Experiment  Station  and  the 
Mining  Department  of  that  institution.  In  1912  he  was  placed  in 
charge  of  the  chemical  laboratory  of  the  Engineering  Experiment  Sta- 
tion. He  resigned  that  position  in  1913  to  accept  another  with  the 
American  Water  Works  and  Electric  Company  of  Xew  York.  In  the 
fall  of  1916  he  left  this  company  to  enter  the  University  of  Illinois  as 
a  graduate  student  and  assistant  in  chemistry,  receiving'  a  degree  of 
Master  of  Science  in  1918.  For  nearly  two  years  he  has  been  chemist 
for  the  Illinois  State  Water  Survey. 


THIS  BOOK  IS  DUE  ON  THE  LAST  DATE 
STAMPED  BELOW 


AN  INITIAL  FINE  OF  25  CENTS 

WILL  BE  ASSESSED  FOR  FAILURE  TO  RETURN 
THIS  BOOK  ON  THE  DATE  DUE.  THE  PENALTY 
WILL  INCREASE  TO  SO  CENTS  ON  THE  FOURTH 
DAY  AND  TO  $I.OO  ON  THE  SEVENTH  DAY 
OVERDUE. 


.'*N  26  1935 


LD  21-100m-8,'34 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 


